From what I can gather, this started happening when ActionQueue was updated to use the custom ExecutableLists (in 7bca11a5047e5346c10779d7d663e63f7c4ecb25 and, probably more importantly, 31ad26731c84e96d532755e1e45f1ffc4ae1674b.

When comparing EntityUpdateActions, if the entity name is the same, EntityAction tries to compare the identifiers, which will call AbstractType.compare(), which is going to blindly cast the possibly non-Comparable ID to Comparable and blow up all over the place.

Even if the behaviour is expected and there is a requirement which I don't know about that all user-type IDs should be Comparable, I guess it could inform the user of that right away when loading the type definitions instead of lying in wait until production

Test case attached.