Heart rate not working when doing out door run

i have an Apple Watch 7 45mm with OS 10.3.1.

for my last 3 outdoor runs, the watch couldn't read my heart rate for 10 minutes in a row.

i went for an hour run and the watch read the heart rate for 33 min and the reading was incorrect. it said my heart rate is at 185, that is too high, not right... then it says it's 137 which I know it correct but it cant seem to stay locked in the heart rate. it keeps going out can't read it for a long period.

how can I fix this? i wear the watch snug, not lose. there is no damage?

do I need to delete all the data from my apple health app? can you even do that? i would like to have clean data and having the heart rate correct is the basic for getting the right stats.

any help will me appreciated!