Undo after disconnecting a target pin will cause a series of internal compile errors

Undo after disconnecting a target pin will cause a series of internal compile errors

User Description:

I've run into what I think is a bug when attempting to compile a blueprint after mistakenly breaking a pin link and then hitting Ctrl+Z to undo. It's only happening in one pair of nodes in a particular blueprint, but they work fine beforehand and when recreating them manually after the error. Searching the hub shows a few other people with related issues, but the reports are either very old or were caused by scripting oversights, where this issue consistently appears and doesn't seem related to my game logic.

This is happening in a binary build of UE 4.10.4, from the launcher, specifically version 4.10.4-2872498, but I've just tested 4.11 Preview 7, version 4.11.0-2896623 (also binary through the launcher), and found the same

1. Open the attached test project
2. Open the 'SideScrollerCharacter' BP
3. In the Event Graph, pan right until the 'Volleyball Set' node is in view
4. Right below that, Alt-click the 'Current Ball' node pin to disconnect it
5. Compile the bp (it will error, which is expected)
6. Press Ctrl-Z to undo
7. Notice the pin doesn't actually reconnect
8. Manually reconnect the 'Current Ball' pin to the 'Volleyball Set' Target
9. Compile

Results: The editor will throw a series of internal compile errors and ask to please contact the Blueprints team

Expected: For the pin to reconnect on Undo and the editor to compile without error

Blueprint internal compiler error after undo