Slow Windows 7 VM shutdown when there is no internet

Question

I have windows 7 Ultimate x86 running in a Virtualbox 6.1.40 guest on a Windows 10 x64 21H1 host. The Windows 7 guest is connected to the internet through the hosts connection via the bog-standard bridged adaptor in VirtualBox.

Now I've noticed that the Windows 7 guest takes a heck of a lot longer to shut down without its internet connection than when it does - about 8 seconds with a connection and just over a minute without. It looks like some kind of internet related timeout thats set at a minute is at play here, any ideas where to look? I've tried all the usual common Windows 7 slow shutdown 'fixes' like lowering WaitToKillServiceTimeout in the registry and it makes no difference. None of the fixes seem to mention internet connection?

UPDATE - Enabling verbose messaging shows that its 'Avast Antivirus service' thats responsible for the slow shutdown as I have latest Avast Free 22.12.6044 (build 22.12.7758.764) installed in the VM.

Looking at the Avast user forums, it looks like an intermittent problem that occurs with certain versions, keeps getting fixed and keeps subsequently returning with the applications update cycle? Not much help other than that.