Hello,
only this table is in suspect mode, I won't suggest to do a restore from backup right now, but it might be necessary.
My suggestion would be that you will open an incident with Product Support and send them the errorlog, where the alter database failed and where the dbcc dbrepair failed. They should take a closer look where in the code this happens, the ASE version you use is pretty new and stacktraces shouldn't happen.
So your problem is indeed that a shrink database failed and one table cannot be accessed, it could be possible that we just rebuild this single table, but as suggested engineering should take a look into this. To save time you might decide to load a backup, not sure what system this is and how important you need to get this online.
Sorry.
With kind regards
Stefan