One of the reasons might be that you are using non-recommended hardware !I'm at a loss to understand why the FreeNAS is so finic
The ReadyNAS that you purchased came with hardware that ReadyNAS knows will work. With FreeNAS, you chose non-recommended hardware. So the onus is on you not on FreeNAS.I really don't have the same level of confidence in this FreeNAS as I did with the ReadyNAS Pro. The latter has been with me for 6 years (and counting) now and not a single hiccup.