Omega 2254.50 Running Slow

Sorry for the long post, but just wanted to share and get input from the group. After selling my 2254 last year, I was really missing it and managed to score another one from the Bay last week. The seller advertised it as recently serviced by an AD in Kansas in January earlier this year. The seller also provided a receipt to show it was serviced at a cost of $550. I thought it was unusual that the AD serviced it and didn’t send it to Omega? Any way, the watch is running about -7 spd and this was not disclosed in eBay description. I let the seller know I wasn’t happy with how the watch was running. He further disclosed that it started running slow on him in October. He took it back to the AD and it was regulated under warranty. The seller said he took the AD for his word that it was fixed and after having it repaired decided to list it for sale. I believe the seller is being truthful, but decided to sell it after realizing it was still running slow after getting it back from the AD. The seller did provide receipts for the full service and also for the warranty service from the AD. The receipts don’t indicate the watch serial number, but the inscription inside the case back does indicate some type of service was performed in January. I have decided to keep the watch and not return it since it’s in pretty decent shape and came with box and papers. I have a Timegrapher app on my phone which is reading -17 spd and amplitude of 333. Obviously this is just an app and I realize it needs to be put on a professional grade Timegrapher. Do you guys think this was just a case of a botched service? Maybe the AD didn’t really service it but only regulated it? Should I just wear it and not worry about it and see if it straightens out? I have posted photos and would appreciate input. Happy New Year to everyone in this awesome group.

I would send it to Omega service center, they'll do a proper service with a two year warranty.

Does anyone have an idea what C.O.A + stands for?

Competently serviced is key. I will wear it for a while and send it off to Omega in a few months. I doubt even an AD can get the parts needed for a proper service these days and all was done is a clean and oil for $550. There wasn’t any spare parts included with the sale.