So the upgrade went smoothly up unto this point. On a production deploy to one of our instances we started having indexing issues which lead me to find thousands of errors in the logs. The code below though has worked since V8 but not in V13.0.3. The errors were all very similar around key1 (culture) being null. The error is hit when trying to access the field Tags (IEnumerable

var basePageComp = (IBasePageComp)node;
tagsContent = basePageComp.Tags;

The error being:

System.ArgumentNullException: Value cannot be null. (Parameter 'key1')
   at Umbraco.Cms.Core.Collections.CompositeStringStringKey..ctor(String key1, String key2)
   at Umbraco.Cms.Infrastructure.PublishedCache.Property.CacheValues.For(String culture, String segment)
   at Umbraco.Cms.Infrastructure.PublishedCache.Property.GetValue(String culture, String segment)
   at Umbraco.Extensions.PublishedPropertyExtension.Value[T](IPublishedProperty property, IPublishedValueFallback 
   ublishedValueFallback, String culture, String segment, Fallback fallback, T defaultValue)
   at Umbraco.Extensions.PublishedContentExtensions.Value[T](IPublishedContent content, IPublishedValueFallback 
   ublishedValueFallback, String alias, String culture, String segment, Fallback fallback, T defaultValue)
   at ...Models.Generated.BasePageComp.GetTags(IBasePageComp that, IPublishedValueFallback publishedValueFallback) in 
   ..\Models\Generated\BasePageComp.generated.cs:line 455
   at ...Models.Generated.Home.get_Tags() in ...\Models\Generated\Home.generated.cs:line 223
   at ...Components.Indexing.SearchContentIndexer.SetTagField(IndexingItemEventArgs e, IPublishedContent node) in 
   ..\Components\Indexing\SearchContentIndexer.cs:line 352