Activity not recording correctly / Watch series 5

About a week ago I noticed that my usual morning 20+ minute walks which previously recorded 18+ minutes of exercise now is recording only a few minutes of exercise. I’ve already recalibrated my watch and done a 20 minute “outdoor walk,” it’s up to date on OS, I’ve restarted my watch and my iPhone. The only thing left is to unpair and repair. What is causing this issue and is there a fix coming? It’s still recording 3 minutes of exercise on my 20 minute walk. I’m walking about the same pace as usual - just over 3mph.