I had the same issue and asked about it on the aws-tools-for-powershell Q&A. As far as I can tell, the answer is you just have to map all the properties. I took the time to do that today. In other PowerShell module contexts, I would expect you'd be able to just pipe in the object from a Get call with changes into an Update call and it would handle the parameter bindings. That doesn't work in this context. This is a known issue for a lot of aws-tools-for-powershell cmdlets according to aws-tools-for-powershell Issue #214.
Below is a snippet of the 66 mappings required to ensure you're updating all properties exactly as they were handed to you in the original Get call. It's possible fewer are actually required, but given I want an exact copy it felt safer to ensure all the data was available and let the API decide what could be dropped.
The etag thing is from: AWS PowerShell update CloudFront distribution
$distribution = Get-CFDistribution -Id $distributionFromList.Id
$etag = $AWSHistory.LastServiceResponse.ETag
$params = @{
Id = $distribution.Id
Verbose = $true
IfMatch = $etag
Aliases_Item = $distribution.DistributionConfig.Aliases.Items
Aliases_Quantity = $distribution.DistributionConfig.Aliases.Quantity
AllowedMethods_Item = $distribution.DistributionConfig.DefaultCacheBehavior.AllowedMethods.Items
AllowedMethods_Quantity = $distribution.DistributionConfig.DefaultCacheBehavior.AllowedMethods.Quantity
CacheBehaviors_Item = $distribution.DistributionConfig.CacheBehaviors.Items
CacheBehaviors_Quantity = $distribution.DistributionConfig.CacheBehaviors.Quantity
CachedMethods_Item = $distribution.DistributionConfig.DefaultCacheBehavior.AllowedMethods.CachedMethods.Items
CachedMethods_Quantity = $distribution.DistributionConfig.DefaultCacheBehavior.AllowedMethods.CachedMethods.Quantity
Cookies_Forward = $distribution.DistributionConfig.DefaultCacheBehavior.ForwardedValues.Cookies.Forward
CustomErrorResponses_Item = $distribution.DistributionConfig.CustomErrorResponses.Items
CustomErrorResponses_Quantity = $distribution.DistributionConfig.CustomErrorResponses.Quantity
DefaultCacheBehavior_CachePolicyId = $distribution.DistributionConfig.DefaultCacheBehavior.CachePolicyId
DefaultCacheBehavior_Compress = $distribution.DistributionConfig.DefaultCacheBehavior.Compress
DefaultCacheBehavior_DefaultTTL = $distribution.DistributionConfig.DefaultCacheBehavior.DefaultTTL
DefaultCacheBehavior_FieldLevelEncryptionId = $distribution.DistributionConfig.DefaultCacheBehavior.FieldLevelEncryptionId
DefaultCacheBehavior_MaxTTL = $distribution.DistributionConfig.DefaultCacheBehavior.MaxTTL
DefaultCacheBehavior_MinTTL = $distribution.DistributionConfig.DefaultCacheBehavior.MinTTL
DefaultCacheBehavior_OriginRequestPolicyId = $distribution.DistributionConfig.DefaultCacheBehavior.OriginRequestPolicyId
DefaultCacheBehavior_RealtimeLogConfigArn = $distribution.DistributionConfig.DefaultCacheBehavior.RealtimeLogConfigArn
DefaultCacheBehavior_ResponseHeadersPolicyId = $distribution.DistributionConfig.DefaultCacheBehavior.ResponseHeadersPolicyId
DefaultCacheBehavior_SmoothStreaming = $distribution.DistributionConfig.DefaultCacheBehavior.SmoothStreaming
DefaultCacheBehavior_TargetOriginId = $distribution.DistributionConfig.DefaultCacheBehavior.TargetOriginId
DefaultCacheBehavior_ViewerProtocolPolicy = $distribution.DistributionConfig.DefaultCacheBehavior.ViewerProtocolPolicy
DistributionConfig_CallerReference = $distribution.DistributionConfig.CallerReference
DistributionConfig_Comment = $distribution.DistributionConfig.Comment
DistributionConfig_DefaultRootObject = $distribution.DistributionConfig.DefaultRootObject
DistributionConfig_Enabled = $distribution.DistributionConfig.Enabled
DistributionConfig_HttpVersion = $distribution.DistributionConfig.HttpVersion
DistributionConfig_IsIPV6Enabled = $distribution.DistributionConfig.IsIPV6Enabled
DistributionConfig_PriceClass = $distribution.DistributionConfig.PriceClass
DistributionConfig_WebACLId = $distribution.DistributionConfig.WebACLId
ForwardedValues_QueryString = $distribution.DistributionConfig.DefaultCacheBehavior.ForwardedValues.QueryString
FunctionAssociations_Item = $distribution.DistributionConfig.DefaultCacheBehavior.FunctionAssociations.Items
FunctionAssociations_Quantity = $distribution.DistributionConfig.DefaultCacheBehavior.FunctionAssociations.Quantity
GeoRestriction_Item = $distribution.DistributionConfig.Restrictions.GeoRestriction.Items
GeoRestriction_Quantity = $distribution.DistributionConfig.Restrictions.GeoRestriction.Quantity
GeoRestriction_RestrictionType = $distribution.DistributionConfig.Restrictions.GeoRestriction.RestrictionType
Headers_Item = $distribution.DistributionConfig.DefaultCacheBehavior.ForwardedValues.Headers.Items
Headers_Quantity = $distribution.DistributionConfig.DefaultCacheBehavior.ForwardedValues.Headers.Quantity
LambdaFunctionAssociations_Item = $distribution.DistributionConfig.DefaultCacheBehavior.LambdaFunctionAssociations.Items
LambdaFunctionAssociations_Quantity = $distribution.DistributionConfig.DefaultCacheBehavior.LambdaFunctionAssociations.Quantity
Logging_Bucket = $distribution.DistributionConfig.Logging.Bucket
Logging_Enabled = $distribution.DistributionConfig.Logging.Enabled
Logging_IncludeCookie = $distribution.DistributionConfig.Logging.IncludeCookies
Logging_Prefix = $distribution.DistributionConfig.Logging.Prefix
OriginGroups_Item = $distribution.DistributionConfig.OriginGroups.Items
OriginGroups_Quantity = $distribution.DistributionConfig.OriginGroups.Quantity
Origins_Item = $distribution.DistributionConfig.Origins.Items
Origins_Quantity = $distribution.DistributionConfig.Origins.Quantity
QueryStringCacheKeys_Item = $distribution.DistributionConfig.DefaultCacheBehavior.ForwardedValues.QueryStringCacheKeys.Items
QueryStringCacheKeys_Quantity = $distribution.DistributionConfig.DefaultCacheBehavior.ForwardedValues.QueryStringCacheKeys.Quantity
TrustedKeyGroups_Enabled = $distribution.DistributionConfig.DefaultCacheBehavior.TrustedKeyGroups.Enabled
TrustedKeyGroups_Item = $distribution.DistributionConfig.DefaultCacheBehavior.TrustedKeyGroups.Items
TrustedKeyGroups_Quantity = $distribution.DistributionConfig.DefaultCacheBehavior.TrustedKeyGroups.Quantity
TrustedSigners_Enabled = $distribution.DistributionConfig.DefaultCacheBehavior.TrustedSigners.Enabled
TrustedSigners_Item = $distribution.DistributionConfig.DefaultCacheBehavior.TrustedSigners.Items
TrustedSigners_Quantity = $distribution.DistributionConfig.DefaultCacheBehavior.TrustedSigners.Quantity
ViewerCertificate_ACMCertificateArn = $distribution.DistributionConfig.ViewerCertificate.ACMCertificateArn
ViewerCertificate_Certificate = $distribution.DistributionConfig.ViewerCertificate.Certificate
ViewerCertificate_CertificateSource = $distribution.DistributionConfig.ViewerCertificate.CertificateSource
ViewerCertificate_CloudFrontDefaultCertificate = $distribution.DistributionConfig.ViewerCertificate.CloudFrontDefaultCertificate
ViewerCertificate_IAMCertificateId = $distribution.DistributionConfig.ViewerCertificate.IAMCertificateId
ViewerCertificate_MinimumProtocolVersion = $distribution.DistributionConfig.ViewerCertificate.MinimumProtocolVersion
ViewerCertificate_SSLSupportMethod = $distribution.DistributionConfig.ViewerCertificate.SSLSupportMethod
WhitelistedNames_Item = $distribution.DistributionConfig.DefaultCacheBehavior.ForwardedValues.Cookies.WhitelistedNames.Items
WhitelistedNames_Quantity = $distribution.DistributionConfig.DefaultCacheBehavior.ForwardedValues.Cookies.WhitelistedNames.Quantity
}
Update-CFDistribution @params -WhatIf