Client crash while dual boxing

Anyone else having a client crash while dual boxing lately? Solo client seems fine with no issues but anything dual boxed is bound to crash one of the clients.

I get an error message from the launching process whenever I launch a client, but the client still loads and runs OK. I normally dual-box and sometimes triple-box and have seen no problems other than a bit of jumpy graphics on my ancient PC when triple-boxing. I’m on Linux Mint 17.3.