I currently have a BungeeCord proxy on which 7 servers are connected (6 in 1.12.2 and 1 in 1.13). To allow players to access server 1.13, I installed ViaVersion 4.1 on my proxy to allow players to join in 1.13. Nevertheless, when I want to connect to the 1.13 server via the 1.12.2 server, I get ejected on the 1.12.2 server with this error in the 1.13 server log:

[09:09:32] User Authenticator #1/INFO: UUID of player Aurelien30000 is 88a10822-c3e4-47e8-8f53-1069858fedc4
[09:09:33] [Server thread/INFO]: Aurelien30000[/92.146.119.15:57438] logged in with entity id 297 at ([world]-7293.296251727365, 66.0, 30302.118197604952)
[09:09:36] [Server thread/INFO]: Aurelien30000 lost connection: Internal Exception: io.netty.handler.codec.DecoderException: net.minecraft.server.v1_13_R1.ResourceKeyInvalidException: Non [a-z0-9/._-] character in path of location: legacy:mc|brand
[09:09:36] [Server thread/INFO]: Aurelien30000 left the game

The only way to access it is to connect directly via BungeeCord, without going through the 1.12.2 server, so there is no error.

Thanks for your help ^^.

Ps : If you need more details, ask me.