Client backpack coregui crash [Persists through respawn]

Tried to move a tool from the 2nd row in the backpack menu, down into the hotbar at the bottom.

That hotbar square then broke and even on respawn it didn’t fix itself.

I can’t select any tool.

After respawn, the broken square overlaps the tool it was positioned over (but was -only- enlarging/shrinking) and it’s all still just throwing this error: