Yep.
I've also had this on my SX-700.
Locks up the whole keyboard often for 4/5 minutes. After that,whatever registration I was playing previously flatly refuses to go. Only solution is to completely power off and re-start. Not impressed.
Maybe related.......Just spent about 30 minutes trying to get rid of some wretched Latin registration that just would not go. Even switching the keyboard off and then on again 4 times, the **** thing was still there. Only went when I unplugged it from the main power, and left it for 10 minutes.
Despite wanting to play something completely different from the Entertainer style section, I couldn't shift it.