God, it seems like every second Rigol scope has some funny intermittent glitch. I get that it could have happened during the conversion, but really, the only mechanisms that could cause funny malfunctions due to the conversion could do the same thing due to a proper firmware upgrade as well.
I second the suggestion to revert back to factory and check. About to do the same with mine, actually. Mine has yet another glitch that nobody seems to have heard of before me.