12.20 update? - Vo2 Max not updating, performance condition has disappeared and erratic HR

Hi, I'm hoping someone can relate to this...

Since 23rd October (perhaps coinciding with the update to 12.20?) I've noticed that Vo2 Max readings aren't updating on my Fenix6 Pro.

I've run 3 times this week and on each occasion I've noticed that no performance condition indicator has appeared after 6 or 7 minutes as it usually does and the performance condition data field whilst running is not displaying anything. I've run at a moderate to quick pace covering heart rate zones 3, 4 and 5.

I noticed that my running heart rate zones differed to the generic heart rate zones by 1 and amended this yesterday so that they matched, just in case. Today, however, it was the same story on my run. No new Vo2 Max reading and also, no performance condition either in the data field whilst running or in Garmin Connect afterwards!

I've also noticed that my heart rate spikes considerably about 12 minutes into a run by roughly 25-30bpm with no added exertion on my part on a route I've been running for over a year! It looks like this is also impacting the training load which is still registering but the increased HR is resulting in a much higher load being added than it should do!

Just wondered whether anyone else has experienced any of these issues, has any idea how to fix them and whether this is in fact related to the 12.20 update or something else?

Thanks in advance!