OS 6.6 on Ultra 6:. Not ready for prime time? Do I need more memory? Or...?

Final update (I hope): I re-ran the upgrade from 4.2 to 6.6.1. The NAS has been working perfectly for over a week. What was different this time? (a) all disk were in place already, so no RAID expansion was needed; and (b) I went straight to 6.6.1, not 6.6.0.

I did order more memory, but haven't installed it; I'm still running the stock 1 GB. I wanted to replicate my previous issues first so I could verify whether increasing RAM alone would fix it. But the box has resolutely failed to show any issues at all: no hangups, no unexpected slowness, no failures to respond. I've tried things like running a scrub while launching backups and hitting the NAS with clients, and the system reacted more slowly when all that was going on, but even so: it all worked, and the scrub of 8.8 TB finished within 48 hours (as did the initial full backup, before I started the stress test). Incremental backups run as quickly now as they did on OS 4.

So I either had a subtle corruption during the initial upgrade, or stuffing two new disks in and expanding the volume triggered the problems. But it wasn't low RAM, apparently, and OS 6 seems to be running fine despite my best attempts to break it. I'm going to label it "bug report closed: cannot replicate."

As for the apparent mislabeling of the System and CPU temperatures? I edited /etc/frontview/sensors/ULTRA6.conf and swapped the "System" and "CPU" labels for temp2 and temp3, ran "systemctl restart readynasd", and now the readings in the web UI match the values I expected from version 4.2 (I got the idea from this thread: <https://community.netgear.com/t5/Using-your-ReadyNAS/ReadyNAS-4200V2-OS6-6-1-fan-control/m-p/1219655#U1219655>).