[aria]

All my proxies work when RM is launched normally. However, for some proxies, this error occurs when RM is launched with these arguments.

@echo off
java -jar -Xmx2024m RuneMate.jar -sdk -proxy=[IP]:[PORT]:[PROXY USERNAME]:[PROXY PASSWORD] -login=Aria:[MY PASSWORD]:DARK -dimensions="980x720" -bot="Account creator"
pause

 

[arbiter]

The proxy is likely intercepting the traffic and manipulating/replacing it with something of its own. Pretty common practice for protected gateways. You should investigate that with a simple Java example.