Hello again, trouble shooting is a process, that I personally do not put any limits on, you have a final answer when and only when you have a final, acceptable answer, that solves the problem.
Generally speaking, from thousands of miles away, and blind to what you actually have, those are my initial remarks, initial remarks are very seldom 100% all inclusive.
There is no telling all of the aspects of the problem... my answer so far does cover the *most likely suspects*, after 51 years in this business and thousands of projects.
Since yours is very new system that rules out clogged up coil, but does not rule out a stray hair or insulation
coming loose inside the coil cabinet (maybe a 10% *chance of that, it is somewhat common.)
It is more likely the coil pan is plastic and has a crack in it, or that the condensate line is not level... there many other options, the coil needs to be inspected to which is the case.
Even then it can be a problem, an occasional drip can be hard to find. It is not always obvious.
Beyond that, unfortunately, if you do access the inside of the coil, air flow conditions will be different and affect the leak
I have solutions for all that, but it IS a step by step process.