Have you ever noticed that some controls tend to “bleed” when the user clicks on them more than once? I’ve seen it often with OptionGroups and Checkboxes when the BackStyle has been set to transparent.
Multiple clicks cause pixel bleeding
The easiest “fix” I’ve found for this (besides making the BackStyle Opaque) is to put the following line of code in a user-actionable event (I usually put it in the Click or InteractiveChange event):
This.Caption = This.Caption
This code doesn’t actually do anything, but I have found that it “stops the bleeding”.