Whayever did I manage there???

Anyway, this ambulance has a hard time holding a charge.... I don't know how
much dye I've got in the system (read that as lots) and I've about torn the
bus apart looking for tattletales... nada.... replaced every O-ring...
charged the thing with nitrogen and used soapy water all over the place....

In your case, I would address the leaks you can see and work from there....
If the car jas been converted to use R-134a, we must remember that these
molecules (I am told) are very small molecules - even to the point of being
capable of leeching through some rubber compounds....