This bug is occurring for me a lot lately - I like having certain envelope lanes visible in the TCP, and I typically shrink those lanes down so they're super small while I'm working, and then I'll resize them bigger when I need to do edits... the bug is:
1) click+drag to expand the size of the envelope lane
2) edit the envelope
3) hit command+z to undo a change
4) the change is undone, and the envelope lane size also returns to its previous size
The expected behaviour is that only the change to the envelope would be undone with command+z - the resizing of the automation lane should be its own, separate undo step...
This is in 5.18 (64bit, Mac) but it's been happening for a while.