When nothing else is running looks like it's awaiting mostly for sdb (disk4), this is not conclusive, but if you have a spare you could replace disk4 with it would be the first thing to try, the fact it's only linking at SATA1 is also strange, though that by itself doesn't explain such a low speed.
Nothing obvious, load average is a little high, but appears to be dropping, likely since you stopped the dockers, VMs, just to try and confirm it's not a disk you can install the systat package from nerd pack, then post the output of:
sar -dp 5 5
Could also be a power/connection problem, check all connections and re-sync parity, if it happens again try with a different PSU if you have one available.
May 30 02:37:46 Skynet kernel: ahci 0000:03:00.1: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0010 address=0xcdf34000 flags=0x0000]
Looks like the typical Ryzen onboard SATA controller problem, BIOS update might help but best bet might be using an add-on controller.
All indications so far are that Dell servers can run with vt-d enable without issues, to do that see here:
https://forums.unraid.net/bug-reports/stable-releases/after-i-upgraded-to-6102-my-network-interfaces-dissappeared-r1956/?do=findComment&comment=19584
May 30 16:51:12 NAS kernel: macvlan_broadcast+0x116/0x144 [macvlan]
May 30 16:51:12 NAS kernel: macvlan_process_broadcast+0xc7/0x110 [macvlan]
Macvlan call traces are usually the result of having dockers with a custom IP address, switching to ipvlan should fix it (Settings -> Docker Settings -> Docker custom network type -> ipvlan (advanced view must be enable, top right))
My supposition was based on the cases found so far, all had vt-d enable and the only common hardware, besides a lot of Intel devices which seemed unlikely to me as the source of the problem or there would be a lot more affected servers, were the NICs, can't say why your server is not affected, but @Thorstenjust found what looks like the exact same issue reported in Ubuntu:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1970453
This should hopefully help get to the bottom of the problem.
00:17.0 RAID bus controller [0104]: Intel Corporation Device [8086:43de] (rev 11)
DeviceName: Onboard - Other
Subsystem: ASUSTeK Computer Inc. Device [1043:8694]
No SATA controller being detected, only this, see if there's an option in the BIOS to change it to AHCI/SATA
Should be OK to re-enable the NIC with that server, see below how to:
https://forums.unraid.net/bug-reports/stable-releases/after-i-upgraded-to-6102-my-network-interfaces-dissappeared-r1956/?do=findComment&comment=19584
You can also check this post for more info about this issue:
https://forums.unraid.net/topic/124108-unraid-os-version-6102-available/?do=findComment&comment=1132815