Ssl3_get_record:wrong version number with large files on Windows

Hello everyone.

I have a synch issue with my Nextcloud client (Version 2.6.0stable-Win64 (build 20190927)) on Windows 10.
As long as I sync only the folders on my server with smaller files everything works smootn.
When I start adding a 2GB folder to the sync I get the failure message:
ssl3_get_record:wrong version number

Odd thing … using my mobile or another WIndows 10 PC works.

Not to forget, this happens while being connected over my home WLAN to my home NC server on the same FritzBox router.

If anyone has a hint, where to look for the problem, I’d be happy.

Short Update: I tried again just out of curiosity to sync my large files again today … and it worked.
I didn’t change anything.
Now I’m really puzzled :thinking:

Although the topic seems to be “solved” for the moment I’d be happy for any hint to understand what was going wrong.
Might it be a bandwidth issue of my home network or router?