Ruby on Rails AWS Opworks creates encoding incompatibility utf-8 and ascii-8bit

Question

I have some code which looks up domains in a database via DNS to get the SPF and DMARC records - the code works flawlessly on cloud9, but when deployed to an EC2 instance on AWS (created using Op works) the same code throws the error below - I am now stuck, I have tried everything to ensure everything is UTF-8 encoded. Mysql DB is definitely utf-8 encoded and I have tried to force utf-8 encoding of the variables as you can see form the code - maybe I am not understanding the error message properly?

Code

<h1>Domain Update scan</h1>
<p>RUNNING</p>

     <% Resolv::DNS.open do |dns| %>
        <% @domains.each do |domain| %>
         <% host = domain.domain %>
         <% host.force_encoding('UTF-8') %>
         <% records = dns.getresources(host, Resolv::DNS::Resource::IN::TXT) %>
         <% records.each do |record| %>
            <% txt = record.strings.join %>
            <% txt.force_encoding('UTF-8') %>
                <%  if txt.include?('v=spf1') %>
                  <% domain.update_attribute(:spf, txt) %>
                  <% domain.save %>
                <% end %>
            <% end %>
           <% hostd = "_dmarc.#{host}" %>
                 <% recordds = dns.getresources(hostd, Resolv::DNS::Resource::IN::TXT) %>
                <% recordds.each do |recordd| %>
                 <% txtd = recordd.strings.join %>
                 <% txtd.force_encoding('UTF-8') %>
                  <% if txtd.include?('v=DMARC1;')%>
                   <% domain.update_attribute(:dmarc, txtd) %>
                  <% domain.save %>
                  <% end %>
                <% end %>
         <% end %>
     <% end %>
 <p>Finished</p>             
 <%= link_to 'Show Domain', domains_path %>
<%= link_to 'Run Scan', domains_scans_path %>                    

ERROR MESSAGE FROM EC2

I, [2017-10-21T16:02:49.832304 #6039]  INFO -- : Started GET "/domains/scanonedomain" for 84.92.56.31 at 2017-10-21 16:02:49 +0000
I, [2017-10-21T16:02:49.834128 #6039]  INFO -- : Processing by DomainsController#scanonedomain as HTML
D, [2017-10-21T16:02:49.835289 #6039] DEBUG -- :   User Load (0.4ms)  SELECT  `users`.* FROM `users` WHERE `users`.`id` = 1 LIMIT 1
D, [2017-10-21T16:02:49.837043 #6039] DEBUG -- :   Domain Load (0.7ms)  SELECT `domains`.* FROM `domains`
I, [2017-10-21T16:02:49.845188 #6039]  INFO -- :   Rendered domains/scanonedomain.html.erb within layouts/application (9.0ms)
I, [2017-10-21T16:02:49.845440 #6039]  INFO -- : Completed 500 Internal Server Error in 11ms (ActiveRecord: 1.1ms)
F, [2017-10-21T16:02:49.846542 #6039] FATAL -- : 
ActionView::Template::Error (incompatible character encodings: UTF-8 and ASCII-8BIT):
     5:         <% @domains.each do |domain| %>
     6:          <% host = domain.domain %>
     7:          <% host.force_encoding('UTF-8') %>
     8:          <% records = dns.getresources(host, Resolv::DNS::Resource::IN::TXT) %>
     9:          <% records.each do |record| %>
    10:             <% txt = record.strings.join %>
    11:             <% txt.force_encoding('UTF-8') %>
  app/views/domains/scanonedomain.html.erb:8:in `block (2 levels) in _app_views_domains_scanonedomain_html_erb___1736845507882839174_20151860'
  app/views/domains/scanonedomain.html.erb:5:in `block in _app_views_domains_scanonedomain_html_erb___1736845507882839174_20151860'
  app/views/domains/scanonedomain.html.erb:4:in `_app_views_domains_scanonedomain_html_erb___1736845507882839174_20151860'