Hi all
I recently bought a new construction custom home that was half finished before the previous owners ran out of money.
There are 2 hvac units that were installed in the attic that were brand new .
One is a 3 ton Payne high efficiency condensing unit.
The other is a Carrier 5 ton unit.
Both had the new line sets ran outside. The house did not have any condensers.
House sq ft is 3700 single story.

I was refered to a HVAC pro by a good family friend and had this man purchase Rheem condensers for both units.
He installed the condensers and the 3 ton has run great. blows very cold air all day long.
The 5 ton initially blew cold but after a week, no more cold air. He discovered a small leak from where he brazed the line set in the attic and then fixed it. Recharged with freon and it again worked great.... for about a week.
HE came back and added more freon. Same story, after about 1.5 weeks, no more cold air.
He has added a dye to the line set but claims no other leaks. He says he will come out and start tearing things apart to look for the problem.
This "pro" doesn't instill a lot of confidence with me. But I've paid him and money is tight after completing the construction of my new house so I don't want to have to pay to have another guy come out.

So my question is this:
What would be the diagnostic punch list to find out wher/why freon is leaking. I'm concerned the line set has a pin hole leak. Even though I triple checked to make sure the nail guards were in place to protect it.
At this point, if it were the line set, there is no easy way to get a new one out to the condenser.

Can't the guy cut the line set in the attic and then pressurize it? If pressure held, then that would isolate that portion and he could move on the other things.

Thanks for all your help!