Problems with HTTP/2 on nginx for Windows?

I am using nginx 1.17.10.1 Unicorn build from http://nginx-win.ecsds.eu/ and Apache/2.4.43 build from Apachelounge on Windows Server 2012 R2.

Nginx serves static files and proxies Apache responses for PHP scripts. Everything was fine until recently.

Two times in a day without any distinct reason the websites stop responding. Memory/CPU/Network usages are ok. Apache starts logging like

XX.XX.XX.XX 0ms [01/Jul/2020:05:05:20 -0700] "-" 408 - "-" "-"

for each request.
Nginx log shows

2020/07/01 06:04:54 [error] 11800#12192: *5002230 WSARecv() failed (10053: An established connection was aborted by the software in your host machine) while reading response header from upstream, client: YY.YY.YY.YY, server: example.com, request: "GET /the/url/here HTTP/2.0", upstream: "http://XX.XX.XX.XX:8181/the/url/here", host: "example.com"

Server reboot doesn’t help. I can connect to the backend directly and it serves the response without any problem.

The only way I could resolve the problem was to switch HTTP/2 off in nginx configuration.

So what can cause this behavior?