inexplicable epoll delay

Hello everyone
I use nginx server as a load balancer/
I've just encountered Nginx introduces a delay 5 seconds.

Access log:
192.168.10.86 - - [24/Sep/2020:12:37:58 +0300] "POST .. HTTP/1.1" 200 0 "-" "-" "-"
192.168.10.86 - - [24/Sep/2020:12:37:58 +0300] "POST ..200 0 "-" "-" "-"
192.168.10.86 - - [24/Sep/2020:12:37:58 +0300] "POST .. 200 0 "-" "-" "-"
192.168.10.86 - - [24/Sep/2020:12:37:58 +0300] "POST .. 200 0 "-" "-" "-"
192.168.10.86 - - [24/Sep/2020:12:37:58 +0300] "POST .. 200 0 "-" "-" "-"
192.168.10.86 - - [24/Sep/2020:12:38:04 +0300] "POST .. 200 0 "-" "-" "-"
192.168.10.86 - - [24/Sep/2020:12:38:04 +0300] "POST .. 200 0 "-" "-" "-"
192.168.10.86 - - [24/Sep/2020:12:38:04 +0300] "POST .. 200 0 "-" "-" "-"
192.168.10.86 - - [24/Sep/2020:12:38:04 +0300] .. 200 0 "-" "-" "-"
192.168.10.86 - - [24/Sep/2020:12:38:04 +0300] .. 200 0 "-" "-" "-"

So there were no responses starting 24/Sep/2020:12:37:58 for 6 seconds.

Also I checked nginx log and found:
2020/09/24 12:37:58 [debug] 18718#0: timer delta: 1
2020/09/24 12:37:58 [debug] 18718#0: worker cycle
2020/09/24 12:37:58 [debug] 18718#0: epoll timer: -1
//6 seconds delay
2020/09/24 12:38:04 [debug] 18718#0: epoll: fd:9 ev:0001 d:00007F344DCE31F0
2020/09/24 12:38:04 [debug] 18718#0: accept on 0.0.0.0:443, ready: 0


Am I correct epoll is the cause of delay? How to fix it?

Thanks.