Apple Watch crashing when running

Has anyone else had this problem? Apple are being no help at all. My Apple Watch 5 GPS cellular keeps crashing when I’m using the running workout. I don’t ever have my phone with me when I run. The Watch is always charged but part way through the run for no apparent reason the Watch crashes, when it turns back on it says power reserve and only has 10% battery!! It’s so annoying as I then lose my run.

Ive phoned Apple 4 times about this now. They’ve sent it off for a repair but it came back with no problem. They keep advising the same thing about updates, pairing and unpairing which I do but nothing works. It continues to happen. They are now saying it’s out of warranty and won’t help me. Are other people having this problem. Did anything help? Am I best just going over to Garmin?? I run a lot, everyday. Training for a marathon currently and really need this sorted.