ProTools undo history


I see that sometimes (I haven’t figured out when) ProTools records parameter changes in its Undo History. Sometimes it doesn’t.
Are there any rules to it? What could cause PT not to record parameter changes in its Undo History? Anything my parameter class is missing to have PT always record changes in its Undo History?
I am not sure yet, but it seems that changes from the GUI are generally not recorded, while changes from an external control module sometimes do get recorded.

Any hint, or idea what to look for is highly appreciated!



Maybe it only happens when begin and end parameter changes are sent?


thanks @Anthony_Nicholls, that was my immediate idea as well, but no, the parameter changes are equally embedded in balanced begin and end parameter changes, wether they appear in the history or not. (Its the same routine).