HRM Pro repeatedly disconnects only in running activity (Epix 2, other activites work)

Hey folks, I have searched the forum for quite some while but didn't find any satisfying solution to my problem. Hope anybody has already encountered it and has a solution for me. Would be very happy.

Here it is:

- Using HRM Pro (new battery) on my Epix 2 watch (both have the latest firmware) via ANT+

- I do not have my phone with me when running and I am listening to music via AirPods Pro (Bluetooth)

- I do not have any problems with the HRM connectivity in any of the different activities (i.e. Strength, Bouldering, Hiking, Walking, Cycling) except from all the running activities. In practice, I connect the HRM Pro to my watch and start a run activity and the HRM repeatedly disconnects and reconnects to the watch. Deleting and adding the sensor back again didn't alleviate the problem. However, I do not have this problem in any other activity. Hence, I am currently running using the Multisport activity, which, unfortunately does not give me run dynamics and other metrics. 

Does anybody have a fix for the issue?

Best regards,

Alex