Apple Watch 10 not tracking sleep well (if at all)

I was recently gifted an Apple Watch 10 for my birthday. Prior to putting the new watch on, I was using an Apple Watch 5. Sleep was tracked every night fairly accurately in terms of when I went to bed and when I woke up. The new watch is running OS 11.0.1, the old watch OS 10.6.1. The problem I’m facing, is that the new watch doesn’t seem to track sleep very well, if at all. For example, Sunday night was the first night I wore it and I was in bed at around 10pm till just before 9am with a migraine. Sleep tracked from 1:17am to 8:42am. Monday night (Tuesday morning) I went to bed around 1:10am, sleep tracked from 3:31am to 8:47am. Tuesday night I went to bed around 10:30pm and sleep shows as a faint block (no split of stages) from 11:17pm to 1:35am, nothing from 1:35am to 3:16am then tracked again from 3:16am to 8:50am. It didn’t track at all last night (Wednesday night to Thursday morning). I’ve not changed anything about how I wear the watch. It’s on my non dominant hand (left), the strap I wear isn’t too loose or too tight, it’s charged enough before i go to bed. It’s really disappointing that a 4 and a half year old watch tracks my sleep better than a brand new watch. Is this a known issue with anyone else? Is there anything I can try to fix it?

[Edited by Moderator]