Welcome to TVPaint Community forums !

Undo is not working or restricted once I grap&use the pen brush selection.
Undo & redo is working on other action, drawing above through the selection , but It's not working on selecting itself.

oh, It's not.
It's working but the one stroke is counted as countless action.
so there's gonna need to undo many times in undoing one stroke.

Thank you for your feedback.
The dev team was able to fix this bug for the next update.