Fenix 5 Plus update 19.10 - HR inaccuracy

I updated to 19.10 through Garmin Express about 4 weeks ago. Since then, the HR sensor has been very inaccurate during running activities. It appears to be picking up my cadence rather than my HR. I had no issues with the HR sensor on the previous software build, but it's now completely unreliable. Is there anything I can do to fix this? Thanks.