Hi Astra,
I haven't got a diesel, and I haven't had you problem, but I do feed my VF860S straight from the 12 volt battery with a separate cigarette lighter socket and an on/off switch, bypassing the ignition key.
I do this to keep the camera rolling when I am away from the vehicle e.g. \I am in a shop etc.
If Jokiin and Flag97 experience with diesels turns out to be your problem (and it looks very promising) then bypassing the ignition switch like I do could be your answer.
My solution does require you to remember to switch it on before moving off and switch it off when you finish for the day.
If you want to use motion detect all night you may consider feeding the dashcam from a jump starter cigarette lighter outlet to avoid having a low battery in the morning.
It would supply a supply a voltage unaffected by anything else!
Getting a firmware changed and having it stable seems to be pretty impossible with these dash-cams.
I have suggested that Foxoffer/Viofo form part of a user group to air change requests and determine priorities, actions and time-scales.
Neither company show any interest in the suggestion.
Shame really, the hardware is good.
Foxoffer not replying to emails is not on. It is not good business practice. Perhaps you could try mailing Viofo on
support@viofo.com and see if they can prompt Foxoffer to reply to emails.
Viofo support may even be able to advise on your problem.
In my book a product is only as good as the support that comes with it.