Removing a key from a Enum Map variable causes duplicate keys to remain

Removing a key from a Enum Map variable causes duplicate keys to remain. It doesn't seem to happen if the removed key is the first and last key, but only with the middle keys.

For example:

A (Removes correctly)
B (Removes and leaves duplicates)
C (Removes correctly)

A (Removes correctly)
B (Removes and leaves duplicates)
C (Removes and leaves duplicates)
D (Removes and leaves duplicates)
E (Removes correctly)

1. Open the attached test project
2. PIE (Removes the key on event begin play)
3. Press the F-key to Print the remaining keys

Results: When a middle key is removed, the keys that are left will contain duplicates

Expected: For it to remove the key specified and all other keys are untouched