Heart rate problem during activity!

Today I have been in the gym and I have noticed a weird heart rate issue with my watch. During the strength activity, the watch cannot picked up my elevated heart rate just after 50 minutes or so when I finished my training. The avg. heart rate was during activity between 75 -95 and after 50 minutes went up to 115 but I don't think that was an actual heart rate. I had an issue with the heart rate during activity but not as much like now. I'm using the latest beta 2.92 fw. I have tried clean the sensor, tight fit, light fit in my wrist but nothing helped.
Please, Garmin could you finally fix this issue! ciq.forums.garmin.com/.../1450637.png