This has happened to me often for at least two years. I don't have a solution to offer. I just wanted you to know that you are not the only affected user.

Hi Spiros Doikas, hi Brian Jones 

I can't produce this behaviour, not even with 2019 SR2.

I don't recall anyone else having this problem. The only time I've encountered it is with a keyboard that developed the fault that any key could 'stick'. Replacing my keyboard resolved the situation.

Can you test whether it happens using a different keyboard?

All the best,

Alison

Spiros Doikas

Can you tell us which actions are being undone?  There were changes in SR1 but I'm wondering if it has something to do with how many are being selected here somehow (maybe Ali is right with the keyboard..)?  If you use the quick access toolbar dropdown you can see how many are selected and what is being undone: