Welcome to the forum, and sorry ofr the delay. The VIM is a pretty simple device and it can only really leak for a few reasons. The picture you showed is a substainila leak, and the main reasons I have seen that happen are:
turning the tank anti-clockwise to remove - the tank should always be turned clockwise, if you turn anti-clockwise to remove the tank, whiich, is the natural thing to do, over time the mouth tip (topcap) will loosen, this releases the pressure in the tank, and it will leak.
The next thing is the fill holes are designed for a needle nose bottle, using a thick nozzle can move the seal and if you're not careful it can be over the chimney when filling, then floods straight out the bottom of the tank, you can fill it thicker nozzles if you are careful, but I would suggest using a thinner one around 3mm or less
the other thing that can cause leaking is the coil not seated correctly, make sure it screwed in fully and over filling but these are fairly obvious..
You can basically test, by taking the tank out, filling it carefully with a needle nose bottle and then replacing the topcap making sure it is fully screwed down, then leave to sit overnight, if there is an issue with the tank the flooding will still occur. The level to whihc it floods is telling, if floods to the top of the coil, that suggests a problem with the seal between the coil and chimney, it it floods right down (the hole tank) then it's a problem with the seal of the coil. If it doesn't flood, it's one of the issues above and something being done in use.
If you could do the following test, then we'll pretty much know the issue and be able to suggest what to do, and if a fault we'll replace the unit.