Armor Piercing Rounds not usable after upgrading to level 5

I have upgraded Armor Piercing Rounds from level 4 to 5. This caused it to disappear from my skill bar and to no longer be assignable. Upon checking it in the skills panel and opening its detail view, it displayed "This information is currently unavailable" rather than the skill details. The layout of the "Always attack without moving" and "Used with weapon set" UI elements was also messed up, they all rendered in one line on top of each other. Selecting a different skill and going back to AP Rounds causes the skill panel to still display the previously selected skill.

AP Rounds had Chain and Pin linked to it when I upgraded it, in case that's relevant.

Bug report reference number 3.700.939.138

Edit: After replacing my weapon, I realized that I only met the strength requirement through the stats on the weapon. Maybe that is relevant too. I'm reasonably sure I had enough strength while the bug happened, but maybe something got krangled in the game logic when calculating the updated stats.