Style not found: cannot find symbol variable

Question

When I try to set a theme for my app with setTheme(R.style.myStyle); I get the following build error (for all of my styles):

error: cannot find symbol variable myStyle

The style is defined in styles.xml as followed:

<style name="myStyle" parent="Theme.AppCompat.Light.DarkActionBar">
    <item name="android:colorBackground">@color/bg_grey</item>
    <item name="android:textColorPrimary">@color/primary_font_color</item>

    <item name="customPrimaryColor">@color/primary_color</item>
    <item name="customSecondaryColor">@color/secondary_color</item>
</style>

The color references are defined in attr.xml:

<resources>
    <attr name="customPrimaryColor" format="reference|color" />
    <attr name="customSecondaryColor" format="reference|color" />
</resources>

The actual colors are defined in colors.xml:

<resources>
    <color name="bg_grey">#F8F8F8</color>
    <color name="primary_font_color">@android:color/black</color>

    <color name="primary_color">@android:color/black</color>
    <color name="secondary_color">@android:color/white</color>
</resources>

I don't know if it is worth mentioning, but the app applies different themes/styles depending on the bluetooth hardware it is connected to. So there are different styles, which use the same color references but with different colors. Example in addition to myStyle:

<style name="myStyleTwo" parent="Theme.AppCompat.Light.DarkActionBar">
    <item name="android:colorBackground">@color/bg_grey</item>
    <item name="android:textColorPrimary">@color/primary_font_color_two</item>

    <item name="customPrimaryColor">@color/primary_color_two</item>
    <item name="customSecondaryColor">@color/secondary_color_two</item>
</style>

Colors for myStyleTwo are defined in colors_two.xml:

<resources>
    <color name="primary_color_two">#004E93</color>
    <color name="secondary_color_two">@android:color/white</color>
    <color name="primary_font_color_two">#004E93</color>
</resources>

I have already tried:

• clean - build
• invalidate caches
• check for duplicates
• migrate to AndroidX
• tried different gradle versions, SDKs, AndroidX and support library versions

If I ctrl + click on R.style.myStyle, Android Studio finds and navigates to the declaration of the style, but when building I get the error mentioned above.

Please help me before I lose my sanity.