Platesolving single slice of a stack results in broken icon

[keastrid]

I've noticed this for a while, but could determine exactly what caused the problem, but now I see the scenario as follows:

Open a stack.

Plate solve only a single image in the stack by disabling "Process Stack":

When the plate-solve is successful and finished, the plate-solve icon stays "depressed":

Clicking on the plate-solve icon to attempt to stop the plate-solve and return the icon to the "undepressed" state results in this error message: