Welcome to the forum onestout.
I am not familiar with Vava systems, but erratic recording are often to blame on 3 tings.
1: use of a alternative power source, or a power source on the way out ( this could also be use of a poor quality USB cable ) ( this you can usually test by using the provided power source )
2: the memory card. These do not last forever, i have even had good brand ones die on me before i was able to fill the just 64GB card once. generally though i do get a few ( 2 - 3 ) years out of a memory card if not more. But i also just drive 15 minutes or so a day on average, if you drive more you of course record more and so wear out the card faster as they have a set number of full read / write cycles.
3: the wire to the rear camera compromised in some way, so if you have a 2 channel system try and pull the plug for the rear camera at the front unit to see if that change things for the front camera working alone.
So it is worth testing the card for errors and read & write speeds, there is a little free tool called H2testw or the SD Orgs own SDformatter tool that will just format the whole card, you will want to run the full format test.
Of course if you only have one of those silly little USB/memory card adapters that come with some dashcams then you will not get the full speed of a fast card as they are simple not able to do that, for that to work you will need a fast USB 3.0 or better card reader plugged into a USB 3.0 or better socket in your computer.
There are also other free drive test tools like crystaldiskmark ASO thise should also test your card speeds and report any bad sectors ASO
It could also be a matter of the card not being compatible with the system, this is a fact with all the brands, though some do work with more brand / model memory cards than others ( the brand might have a list of compatible memory cards on their site )
In general i find that most often a none compatible card will work, but when it is filled up it will start to act funny, a card just not wanting to work at all, even if it is functional in other devises, well it is rare i have seen that.
It is important you look at your memory card now and then, play a few seconds of some of the recordings ( i tend to focus on first and last segment in a drive session )
It should not take more than 10 minutes or so doing this, things worth looking at is drive sessions starting or ending in weird places, your drives should start in places you know, and not 1/4 mile down the road from a know place.
Me i am very set, so my places are home - mothers place - friends place - my favorite gas station - my favorite place for shopping, so that is where i expect drive sessions to start or stop.
If you are a working man, then your place / places of work will be in there too. i am retired for health reasons myself so no more working for me.
If you look at the memory card every few months it will be good.
Many / most new models, they will actually sound a alert if it is not able to record for some reason, this was / is a major flaw in old cameras as even the REC LED will be lit up indicating recording going on, even if its not really doing that.
