Hey mate my S70 does the same and its done the same now for ages i have it for it for maybe 2 years.
The tail cap is frigidity mine is probably worse because it has a spring bypass with like 18 gauge wire.
I ended up changing the washer on the tail cap and it helped some what but its still not perfect i actually had no washer holding the switch in place. I am not sure if it didn’t come with one or i took mine out ages ago.
I’ll have a proper look at mine and see if i can find a solution.