Extreme lag experienced with multiple connections from the same IP

[pulpocaminante]

Description

When I'm the only person in my house playing, I experience almost no lag. As soon as a second person connects from the same IP, we both experience horrendous rubberbanding constantly.

Reproduction
Two simultaneous connections from the same IP.

Additional context
Our internet speed is quite good, and the game is only ever really using 2kb/s up, 20kb/s down, so I would suspect this has something to do with how simultaneous connections are handled.

[whatston3]

Haven't been able to replicate the issue - if it persists, reopen this. Thanks.