TRIMP or HRSS? Am I missing something?

I’ve been using TRIMP - for well over a year, with heart rate and power data ( I only cycle) - Today I was looking at my setting and changed it to HRSS and my previous 2 months or so all dived down into the red - high risk zone. I consistently train about 10-15 hours a week - 85/15-ish (Z1/2 and Z4/5).

I was kind of stunned to see that. Switching back to TRIMP and I go back to dipping into the red occasionally.

Am I doing something wrong in the setting? I get data daily from my rides and update my wellness daily.

thanks Mattie B