Are you able to post similar sized file (~461kb) to a different partner system successfully?
What is the protocol used for communication with your partner system ( http/https )?
You mentioned new receiver profile, can you share what are the changes when compared to existing profile ( the one which worked fine ) ?
From the description i suspect the issue is with http method ( post vs get), if the method is set to ‘get’, than it limits the size of data that can be encoded in the url. Changing it to ‘post’ will resolve the issue.
Looks like you captured below mentioned error at default ( 4/info ) log level, increase the log level to 8 / trace to capture more information, which might be useful in troubleshooting the issue.
#B2B-Integration#Integration-Server-and-ESB#webMethods