Hashcat brain "too many clients"

[S_g]

Hi all,

Looking for some advice, i have 4 machines and 5 instances of hashcat doing mask attacks on a hash all started with:
--brain-client --brain-password <password> --brain-client-features 2 --brain-host <host.ip>

They send the attack info back to hashcat brain server running on a single The-Distribution-Which-Does-Not-Handle-OpenCL-Well (Kali) linux machine on the local network.  It works fine for a week or so then one of the hashcat instances will start spitting out

"brain_recv: Bad file descriptor"

and on the brain

" -1 Too many clients".

I checkpoint/kill the offending instance and the brain shows ~30 disconnect messages and keeps happily sending and receiving from the others

The brain machine isn't the best speced, x86. 8 gb of ram,  AMD 4300 Quad-Core. 

The hashing machines vary from GTX2080 ti's, to GTX 970's. 

I'm leaning towards some form of networking problem with the "Bad file descriptor" message.  My next step is to packet capture the traffic next time it happens to see what is going on there.

But if anyone has seen this before and can save me some time i'm open to all advice.

Cheers.