Bug: Creation of multiple instances when replacing a UMG widget

When I try to replace a UMG widget I end up with hundreds of variable of the same widget

The first button you see in the third image is actually one of my attempts to reproduce the bug. I deleted all the widgets in the canvas panel but that reference didn’t go away.
It seems to happen with all the common and user created UMG elements. It doesn’t seem to happen with panels.