I have exact same issue. But I cannot still found solution.

The main problem is this device UUID, which did not change until the last update, why did it need to be changed in the last update. Besides, its peripheral UUID is needed to connect to a device. In order to connect without scanning, a fixed UUID is required. So as you suggest, it is not possible to connect with the serial number of the device. If this UUID doesn't function the same as the MAC address, why doesn't iOS give us the fixed MAC address? All bluetooth apps and tools use MAC address as uniqueId on Android and UUID (remoteID) corresponding to MAC address on iOS. As I mentioned above, I have never seen this UUID change in any update (just as it should). Until the last update. This will put many app developers (including me) in a difficult position and will force many apps to make mistakes (like mine). As a result, every bluetooth device has a uniqueId (MAC address) and it is necessary to be able to use this ID. I think iOS also needs to provide this uniqueID to us developers.