i'm having an odd issue with NFS that i'm hoping someone else might have run into, since i can't find any information on the Internet... so i have an NFSv4 export on a FreeBSD server mounted on macOS ...

Your array is RAID-6, which performs relatively poorly with small atomic writes. Your NFS file-system is set up as SYNC, which means that the I/O has to get to the server's disk before the write is ...