@alter_ego_uk:
Could you please send us the exact step-by-step reproduction of the error?
What kind of Midi-track did you freeze and what instrument did you use?
Also, please send us a test project where you get such errors to be able to investigate the problem.
@Kidzley & Crabman
Did you read the text “Limitations of IAA”? Please close all apps as it is written there and try again.