The whisker menu just turns into a black box until I move the mouse over it which turns it back to normal
Created attachment 6707 The black box in the whisker menu This is what the box looks like.
UPDATE: The black box appears when I move the tabs around in the panel
What panel version are you using? This bug was caused by the Xfce panel, not Whisker Menu, and was fixed with version 4.12.1
Sorry my bad. I misassigned the bug to whisker when it should have been closed instead...
As mentioned by Graeme, this was fixed in 4.12.1. Please reopen if you can still reproduce it with 4.12.1