ActiveX ComboBox Completely Stops Working

I had a bunch of ComboBox form controls that I switched over to ActiveX controls so I could change their color. However, now when I share the workbook, they'll eventually fail. It's not usually immediately, but eventually I'll open the file and they're broken. (NOTE: It may not be linked to sharing)

By not working I mean I can't even click on them. Even if I unshare the workbook and try to view their properties, it gives me the properties of the worksheet instead of the ActiveX control. This usually means I have to delete the control and remake it. I'm super confused.

What am I doing wrong? I really don't want to have to revert to form controls.

EDIT: Autoload and Enabled were both set to true. Neither has an effect on the outcome.
EDIT2: My Trust Center setting for ActiveX is "Prompt me before enabling unsafe for Initialization (UFI) controls with additional restrictions and Safe for Initialization (SFI) controls with minimal restrictions."