Snagging is holding the money hostage
The list never shrinks and the retention sits behind it.
What's happening?
The snag list has become the payer's calendar. Items get cleared on site but never recorded as cleared, new items appear to replace them, and no single agreed version of the list exists, so it never visibly shrinks. While it stays open, making good does not get certified, the closeout documents stay unassembled, and the retention parked behind all of it does not move. Leaving it vague costs the payer nothing; the whole cost of the drift is yours.
The way out is to run the end of the job like a process with deliverables and dates: one list agreed and owned, every item closed with evidence attached, the O&Ms, warranties and certificates scheduled and chased like the valuable documents they are, and each certificate asked for the day its trigger falls. Paperwork releases the money; treating it as an afterthought is what holds the money hostage.
The solution
The closeout run as a process with dates.