@Kastro
I doubt there was ever a 44mm diver. There are 42mm ROOs and divers, 44mm ROOs, and 48mm ROOs (T3/Legacy/Shaq). The Royal oaks come in sizes of 33, 37, 39 and 41mm.
The A7750 sec@12 movement has been improved for the recent batches, and the key issue is friction. A proper service and swiss mainspring replacement will alleviate the friction issue and make the movement run a lot more reliably. One key to remember is to leave the chrono function well alone. Even for genuine AP calibers and LWO movements, the chrono function is not perfectly reliable. So if you are willing to treat the chrono and subdials as perfunctory decorations and avoid using the chrono, you have a much higher chance of having a watch with a long and healthy lifespan after a service. I do not even touch the chrono function on my gen ROOs. Trust me, even on the gen, the chrono function does not have sure-fire reliability.