Brief
A month-end reconciliation instruction that is competent at the work and silent about everything that could go wrong with it. It has been running for two months without incident, which is the usual reason nobody has looked at it.
It also contains one instruction that is worse than silence. You should be able to find it.
Rewrite this so that each of the four situations below has a defined response: an incomplete bank feed, a transaction that maps to no account, a closing variance beyond a threshold you set, and the same transaction appearing twice.
Each response needs a trigger someone else could apply the same way twice. Attach the reason to your prohibitions. Keep the working instructions — this is addition and repair, not a rewrite from scratch — and stay under about 320 tokens.