I had the same error and it was caused by the Text3D plugin not working on 5.6. So, if you used that plugin on any BP or Level, you need to replace them even if they aren’t showing the Text3D element inside.
I had the same error and it was caused by the Text3D plugin not working on 5.6. So, if you used that plugin on any BP or Level, you need to replace them even if they aren’t showing the Text3D element inside.