I'd love to help you out here Dexter, but this is just one of those things that reminds me of how terrible I am at troubleshooting problems I can't put my hands on and see myself.
The only thing I could think of is to rebuild your samba server from scratch.
Yeah. I've reinstalled it and messed around with some settings in pfsense and plex, then the next day the states seem to have sorted themselves out and the process is still sitting at 25%, but that's better than what it was. Not sure if any of it helped or if it's just a coincidence, there was never any immediate effect. So I don't know, it still seems to be doing something that it probably shouldn't be but I can't figure it out.
off topic: if the clients are Linux why not use NFS instead of samba?
I've had issues with nfs before, but I may switch to it, at least for the linux clients
after updating my centos6.x and raspberry pi 2 this weekend...
...they are oddly both using CPU and traffic that they were not using while idle in the past.
nevermind.... looks to be related to someone trying to bruteforce into my ssh server