Quick update: I spoke to Small Business support by phone. They told me the "Fail to delete IPv4 ARP entry" error is normal. They said my RDP problem is a known issue they hope to fix in a future firmware update. The recommendation given to me was...
I also have this problem with an RV130W. This error is continuously logged and end users are unable to connect through an RDP port forward. We're also needing to reboot the device about once a week. If anyone has found a solution, I'm all ears.