Skill level 1 upgrade can be upgrade then refunded and still keep the upgrade. The upgrades do work as normal and not a visual bug. To upgrade to level 2 you still need to use 3 AP. Tested and it work on both normal and street brawl.
The game crashed 2 times today. After the result screen you can still control the character and the enemy killed me. When the match closed and i still on death timer it crash to desktop.