Cloning a DVM: some apps don't start disposably

[tetra...@danwin1210.me]

I have a dispVM `my-dvm` where everything works as it should: if I open
Firefox, that Firefox instance starts in a new dispNNNN VM.

I want to clone that dispVM and create a new dispVM connected to a
different network-providing VM, so I do exactly that: clone `my-dvm` and
set the netVM for `my-new-dvm` to `my-other-netvm`.

When I start XTerm in `my-new-dvm` the new XTerm window starts in a
dispNNNN disposable VM, as it should.

When I start Firefox in `my-new-dvm`, however, Firefox starts up in the
underlying `my-new-dvm` template, not in a dispNNNN disposable VM. This
means that the Firefox browsing history and prefs are saved, any malware
gets to persist, etc.

Comparing the output of `qvm-prefs my-new-dvm` and `qvm-prefs my-dvm`,
all settings are identical except for things that should obviously be
different (the netvm, the GUID, the IP address, etc).

Any idea what the problem could be?

[tetra...@danwin1210.me]

After further testing, the problem does not appear when cloning a Whonix
workstation dispVM -- the problem only appears when cloning a
Fedora-based dispVM.