invalid public key signature

Some users are getting disconnected because invalid public key signature

The thing is that they can join the lobby, they can join another server, but they can't join the 1.19.3 server (yes, I know it's outdated).
It's like 3 users, because others can play fine. I can too. It started happening after installing ViaVersion for 1.20.5.

Anyone had this problem?
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