I do not use ZEOS, but guessing from error message there is update conflict.
So you try update some record in database, but no record for update is found, so ZEOS raises exception.
It can hapen in multi-user environment, where somebody else updates record, which you try update later, but no matching is found.
If it can be your case, then check how update is done if using all original fileds values or only primary key fields etc. ...