No. Contrary to rumors, there was not a run of bad ROM chips in the S90's.

The cause for all this concern that Patch #1 in the S90 was recorded hot - there is 32db of gain at 6kHz. This is the only patch that is affected and it is entirely possible to modify the patch, reduce the gain, and save it in a user preset.  The S90 manual covers editing and storing (see p.60 for Voice Edit, and p.73 for the Store function).

Yamaha will very likely address this minor issue in an upcoming software update.