Anyone looked into errors like this one and know something?

Serialization and deserialization of 'EPiServer.ServiceLocation.ServiceAccessor`1[[EPiServer.Core.Internal.ContentFragmentFactory,
EPiServer, Version=12.20.3.0, Culture=neutral, PublicKeyToken=8fe83dea738b45b7]]' instances is not supported.
The unsupported member type is located on type 'EPiServer.ServiceLocation.ServiceAccessor`1[EPiServer.Core.Internal.ContentFragmentFactory]'.
Path: $.SomeContentArea.FragmentFactory.Accessor.
<--- Serialization and deserialization of 'EPiServer.ServiceLocation.ServiceAccessor`1[[EPiServer.Core.Internal.ContentFragmentFactory,
EPiServer, Version=12.20.3.0, Culture=neutral, PublicKeyToken=8fe83dea738b45b7]]' instances is not supported.