SOLVED: Buffering problem

[cifri]

When I play a movie remotely (it doesn't matter if it's Directplay or transode) the playback stutters. There is also a problem with a bit rate that is a fraction of the upload capacity on the server side, and the maximum download speed on the client side is only half used.
The most interesting thing is that if I stop the playback, the download speed of the client triples during the buffering, but as soon as I start the playback, it drops back, so it starts stuttering again as the client's buffer runs out.
In the case of Windows native client and Browser client, the error will definitely exist.
Everything works fine in a local network.

It runs on a Debian server.

[tmsrxzar]

dashboard -> playback -> throttle transcodes; compare with the opposite of what you have set (if on/turn off; if off/turn on)

[cifri]

dashboard -> playback -> throttle transcodes; compare with the opposite of what you have set (if on/turn off; if off/turn on)

I just tried that, without success.
Direct Play also has the problem...

[tmsrxzar]

sounds like a bandwidth problem, have you speed tested your server/client pair external of jellyfin?
put a 1GB.bin in your webroot then pull it to your client with wget/curl and compare with "aria2c -x 4"

[cifri]

I will definitely try it!
It is certain that this phenomenon is due to some network condition. Because if the client machine is connected to a UTP cable, the player behaves as expected. The phenomenon is mysterious because the Wi-Fi signal is strong and so is the Internet speed. The access point is a UAP-AC-PRO, which is quite good, and I walked about 4 meters away from it.
Several family members would use Jellyfin with a notebook.
That's why I'm investigating further to see what the problem could be...

[cifri]

The LAN cable just came out of the AP's power supply and switched to Mesh mode. It remained functional, but caused this strange behavior.