Where can I get a copy of firmware version v18.15 beta? I would like to revert my Forerunner 955 from v18.27 to v18.15 beta, I guess I can then downgrade using Garmin Express?, I don't mind losing data / doing a factory reset if required. Reason: OHR takes way longer to 'acquire' and under-reads for approx 10 minutes at start of run which screws up all the metrics based on heart rate (which is most of the useful ones!). Problem started when upgraded from 17.2x to v18.22, looking at the firmware changes log the 'Improved optical heart rate performance in cold weather." looks like the most likely culprit and so the last version prior to this appears to be v18.15 beta.
