Had something similar a few years ago.
Had a customer who wanted TV/fire looking thing installed - a hole in the wall looking design. With a tight f**k of perimeter (snug fit - no shadow look - as it's on the item already)
Priced it up - happy go ahead etc.
Turned up, no device in the job.
I said not really happy to build and finish while its not here etc.
She said just do it, timing is key.
I said ok, send me a PDF and tech drawing AND the measurements. I received them from her.
I checked her receipt and model number and the tech drawings and measurements. I warned her that if it turns up and is different - it's on her, she agreed and text me to agree and confirm (while I'm there in front of her).
Did it, got it plumb and bang on to the millimetre all round - full day, absolutely bang on.
Week later she had it painted - and the thing turns up and it's 2mm wider than tech drawings stated.
She and hubby checked and checked (possibly looking for a way to blame me) and eventually admitted it was between them and the Chinese suppliers.