It does sound like a freon leak.
Another symptom of a freon leak is if you only get frost on the evaporator coils were the freon enters the coils.
Also the compressor runs all the time except when the unit goes thru a defrost cycle.

The reason I recommend replacing a unit with a sealed system problem is the possible cost involved and no way to tell how high that will be.

First the tech has to find the leak and may spend a lot of time and never find it.
Next the leak has to be repaired and that may reqire a part (evaporator etc.) replacement.
Or if they cannot find it replace the compressor on the gamble that it is leaking.
Also the drier in the sealed system should be replaced.

So costs can go though the roof and you still end up with broken unit.