There is something wrong with the transformations filter. It’s not always reproducible, but mostly after using the slant parameter, the undo function stops working completely. Do you have any hints?
(Version 2.6.7 (1357) plug ins disabled)
I tried it and it worked a few times for me. One thing that is a bit odd is that the result of the undo is only shown when you release the Command key.
I have sent a screen record to support.
Sometimes, after intensive work with many steps, a single undo just goes back to the point before transforming. So all work is lost.