I have been using a Classe SSP-25 for about 18 months and have never had a single problem with it. I love everything about it except it doesn't support a multi-channel analog input.
The SSP-50s had ALOT of problems, which is whay they were only in production for a VERY short period of time. There was a time a few years back when a LOAD of TEST and PROBLEMATIC units were released into public.
I had an 50 and had plenty of problems. When it worked, it was great, when not, it was horrible.
The locking deal was one of the problems. Does yours have a serial number?