Hi @Mikedm 
Unfortunately, we don't actively test our metricbeat on FreeBSD so errors like the one you are describing (specially on the system module) are somehow expected.
Those errors are all about fetching data of the beat itself: resident memory, CPU usage and file descriptors. From what I can see in our code, it's expected to work.
I don't know much about FreeBSD but it looks like something specific of the OS. Maybe permissions, execution or both.
Sorry if I can't help more