Quick thought - how are you launching 'mis'? Are you using 'sudo' to launch it?
I use this useful script to run mis as a service trought systemd:
https://vswitchzero.com/mystic-systemd/
On this script i specified a User so Mystic run as a normal user (i can see this with htop).
Anyway, if it could not find the python modules it would give the module not found error, instead the connection is closed silently.
Another strange thing is that if I launch the command with ./mystic -uUser -pPassword -zSCRIPT.mpy it work.... so it seem something related telnet or server....?!?!?
Finally, in the error log I see this: "MYSTIC 001 An error has occured: EAccessViolation Access violation" both if I use telnet and if I use the local command....
I think that the only one can help us is g00r00 :-(
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Violence is the last refuge of the incompetent!
--- Mystic BBS v1.12 A48 (Linux/64)
* Origin: REtrogaming ACTivities (REACT) BBS (2:335/601)