Apple Watch exercise minutes not registering

Hi everyone,

I own Apple Watch series 3, and noticed 6 months ago that I'm not receiving the correct amount of exercise minutes. I walk the same route every morning, which takes about 40 minutes. Since a software update, I have only been receiving 10 exercise minutes from the same 40 minute walk. Before the update I would receive 40 exercise minutes. My partner walks with me and has an Apple Watch and does receive 40 exercise minutes.

I have tried my own troubleshooting which included unpairing then pairing the watch, erase and reset the watch, erase and resetting the linked iPhone, I have updated to the Watch OS version. I have also checked the historical heart rate data, thinking that my heart rate maybe too low to register exercise minutes, however the heart rate is consistent (92 bpm) throughout the entire walk and hasn't changed since the problem started.

When I check the exercise minutes data, I can see there are big chunks of time during the walk when no data is recorded.

Any ideas?

Thank you.