SMART: Cannot schedule tasks for some devices

My server currently contains 12 different drives, 2 NVMe SSDs, 8 internal HDDs and 2 external USB drives. I've recently replaced an old SSD with a newer one. I use SMART to monitor all of my drives. When I go to SMART -> Devices, SMART monitoring is enabled on all devices, including the new SSD and both of my external USB HDDs. However, when I go to SMART -> Scheduled tasks, the new NVME SSD and one of the two external USB HDDs are not listed. When I want to create a scheduled task for the missing ones, I cannot pick the two missing devices in the device drop-down list. I don't know why.

I've tried to disable monitoring for the two affected devices in the SMART -> Devices section and reenable it. I get random "504 - Gateway Time-out" errors (without further details), the page reloads, device monitoring seems re-enabled. However, I can still not create a scheduled task for the device in question. I've tried the same approach for the other drive. Same result. Running smartctl via CLI succeeds for both devices so obtaining the SMART states by itself should not be the problem.

Any idea what's going on here and/or I could debug further? Any advice appreciated...

Thanks, chente. W.r.t. the NVMe you could well be right: I've bought a very recent Samsung SSD 990 Pro. It seems there have been some firmware issues with it. I'll try to upgrade the firmware in the next couple of days. W.r.t. the USB drive, I'd be surprised. It's an 18TB WDC WD180EDF. I bought it about 2 years ago. The other USB I'm using is its predecessor, a 12TB WDC WD120EDAZ which runs without problems. Same vendor at least. Anyways, I'll look into it. Thanks again, mate!

Yep, did that already. Twice. It was enabled initially, but the devices did not appear in the scheduled task. I then disabled it and renabled it again for both drives under devices, but it did not make a difference: The device was still not selectable when I tried to schedule a task for it...