Baud rate for Ender 3 on Repetier Host (Debian)
Your firmware configuration may vary (probably worth checking what you have set), but from The Ender 3 configuration is set to 115200 baud rate #12174, the standard baud rate seems to be 115200.


  I think the default Ender 3 configuration is aligned to the Ender3 official confg, which has 115200 so...


Ah, but this is Marlin, and you're using Repetier. Hmmm, maybe ignore that then.

According to Recommended baud rate?:


  Normally 115200 or 250000 baud should work find and usb->serial latency is the bottleneck.


Apart from that I don't know. Sorry. I might delete this answer, if it doesn't help.