Screen goes black after saving a long activity.

Hello, 

I had this issue for a while and even hoped that 17.10 will solve the issue, but it did not. (Now I have 17.20, Epix pro 47, Sapphire)

After a long activity like Snowboard or Trail run watch show info about the activity and as soon as I click Done, screen goes back.

I tried to do soft reboot, charge in full, reboot while on charge.

Issue repeats as follows:

watch start to load up with the Epix logo, after start loading maps and in a bit the screen goes black.

Tried to repeat process multiple time (also watch start this process by themself sometime).

But later everything goes back to a normal state in the evening either because watch switch to a night mode or the watch is able to sync via my home wi-fi.

Issue was reproduced several times only in Snowboard or Trail run activities yet. Activity is saved. 

Watch is visible in Garmin connect app and can sync + the latest activity is available online.

What should I do?
Thank you.