Fix

proxy/src/main/java/com/velocitypowered/proxy/command/builtin/SendCommand.java

@@ -83,9 +83,15 @@ public class SendCommand {
     ArgumentCommandNode<CommandSource, String> serverNode = RequiredArgumentBuilder
         .<CommandSource, String>argument("server", StringArgumentType.word())
         .suggests((context, builder) -> {
+          String argument = context.getArguments().containsKey(SERVER_ARG)
+              ? context.getArgument(SERVER_ARG, String.class)
+              : "";
           for (RegisteredServer server : server.getAllServers()) {
+            String serverName = server.getServerInfo().getName();
+            if (serverName.regionMatches(true, 0, argument, 0, argument.length())) {
               builder.suggest(server.getServerInfo().getName());
             }
+          }
           return builder.buildFuture();
         })
         .executes(this::send)