The upgrade activated when I crafted the first level of the skull summon, and when I went to upgrade the skull summon, it bought another copy of it instead of upgrading. Two of the icons appeared at the top of the crafting menu, and two of them spawned but seemed to get stuck targeting nothing (other summons were also targeting the same spot).

I was also unable to interact with the level exit and the game hangs when trying to continue the run from the main menu. Not sure if they were related or just a coincident.

Don't know if there's a better place for bug reports so I'm just posting it here LULE