For example, if you use "Select All" and delete all the redundant links, Undo doesn't bring them back.
You don't have to use Select All to see this bug--simply delete a single link in the Remove Redundant Links Panel, and Undo won't restore it.
I have improved this behavior somewhat in 2.1.1-b9. You can now undo single redundant link deletions. However, if you do multiple deletions at a time, only the last one gets successfully undone.