I agree, I don't believe there is anything!
In which case, I think you need to first establish whether the Zappi is working "properly". Do you ahve a friend/neighbour/relative with an EV (any model) that you could invite to come and test your charger? Simply plugging in for a few minutes, or perhaps longer, should indicate whether it is the Zappi that has a problem delivering a consistent and continuous charge.
If the same problem occurs for this third-party user, you need to "inform" your installer that the unit has a fault and that he is required, under Consumer Law, to come and "sort it"!
If the third-party vehicle charges without problem you need to go back to the supplying dealer and make very clear that your car is NOT "working as it should" and the dealer must investigate what is "wrong".
One other thought: do you have a Granny Charger which you could plug in to the car and see whether the (admittedly rather slow) charge proceeds without error?