To reproduce the bug, do the following:
1) Select "Ignore Replay Skill Selection" in the options menu.
2) Load any level.
3) Select any skill, which is not the first one on the skill bar.
4) Frame-skip back (using larger time amounts, and not only by going 1 frame back per hotkey hit) until the very start, such that one would have frame-skipped into negative time.
5) Observe that the selected skill on the skill bar jumps back to the first skill on the skillbar, while it should stay on the currently selected one.
Fixed for next update.