There are addons that have functionality attached to their minimap buttons that extends beyond the left/right click (a bunch of LDB launchers or feeds for example)

This line MBB.lua:342 breaks them.
I haven't checked the retail version but I'm assuming the same happens there.

If for some reason replacing the click registration is needed at least do this instead.

buttonframe:RegisterForClicks("AnyDown")

so middle / btn4 or btn5 clicks are not ignored.

Thanks for the report. I don’t have wow installed atm. I’d happily merge this change if you’d like to make a Pull request. Cheers, Vall.