Backup problems with Catalina

The following may or may not help?

https://support.apple.com/en-gb/guide/mac-help/mh35860/mac

https://support.apple.com/en-gb/guide/mac-help/mh15139/10.15/mac/10.15

Pay attention to the information at the bottom of the second link.

QNAP's support for Time Machine is here:

https://www.qnap.com/en/how-to/tutorial/article/using-time-machine-to-back-up-your-mac-to-a-qnap-nas-via-smb/

It only mentions High Sierra. MacOS Mojave followed which introduced some major changes and these have continued in Catalina. Perhaps that's where the problem lies? Contacting QNAP support may get you further than here?

Good luck.

Only my opinion but I don't think Time Machine is "enterprise" enough for your needs. Fine for a small network of maybe up to 10 users, really good if its just one or two, but in a school environment? I don't think so. I've installed and deployed thousands of Macs in various educational institutions in the UK and abroad over the years and Time Machine would never have been on my list of back-up "solutions" for any of them.

Before you get any deeper into this and potentially an even bigger mess I would look for something more suited to your needs such as what you're already using for your Windows network.

Time Machine is great for backing up consumer devices. In a business environment with managed devices, using Time Machine to restore data can cause issues with managing the device the data was restored to.

No criticism intended here and I'm truly trying to be helpful but what viruses are you protecting the Macs from? Apart from ticking some legacy policy requirement made (probably) when you had an all PC network, I have to ask where's the common sense in it? Why install something on a platform that's potentially causing back-up issues?

I'm guessing ESET is your MDM for your iOS estate, obviously on the same network with no anti-virus installed. All your PCs will for certain have it installed so why install it on the Macs? If it was me I would re-think the strategy regarding your Macs, disable the A/V and see if TM (if you persist with it) starts working again.

Trojans, viruses, and malware are out there that affect macOS devices. Most consumers have very little vulnerability to these, but businesses and schools are often targeted. We run Cylance on all of our macOS devices. I've used ESET before with no issues, but again, I don't use Time Machine in a business environment.

@ celliott147 - my thanks for reminding me although I already knew this.

However some of my customers include local UK governments and NHS sites - with heavily policed (and I mean very strict) networks - with small-ish (30-100 approx) Mac estates and although they have A/V installed (MacAfee, Sophos etc but not ESET) their Macs have not been targeted and they're not likely to either.

Basically their PCs are far easier targets. Human natures = path of least resistance.

I've been using Macs (and other platforms) for 39 years and in my experience you need a lot of help to get anything truly 'nasty' installed on a Mac. Worst I've seen, in all those years, is the "Leonardo Virus" and the "Auto-Start Worm" back in the early 90s on System 9. The "Virus" amounted to a banner flying across the screen on the 15th of April wishing Leonardo da Vinci "Happy Birthday". Flew across the screen once and that was it. The "Worm" rebooted the Mac when printing. Terrifying!

Admittedly things have moved on and perhaps I've just been (very) lucky but I've not seen anywhere near as devastating since then on any Mac that I've owned, used or support then or now.

My 2p.

We use OneDrive. We have a script to redirect all folders into OneDrive. It's not officially supported and requires a bit of babysitting, but it works. I've also used CrashPlan in the past.