I have a BCD card in a weigh meter going to a TTL card. Sometimes the meter will send a bad string and cause the overflow to max. and fault my CPU. Has anyone seen this?

To stop a maths overflow faulting the processor add an unlatch instruction as the last rung of file 2, this should unlatch S:5/0

Then you need to look at possible problems caused by the overflow, and maybe process only valid values.

Depending on your application it may be worth checking the value remains constant for two scans before accepting it as valid.