Pro.
Following diese's line of thought...
I don't speak Italian, so not sure this will help...but:
Since the 139 was originally a Bell/Agusta project to supposedly replace the 412, this problem sounds very familiar.
The 212/412 had a similar feature in their hydraulic systems whereas if you were a little weak in dialing in the test pressure it would overfill the reservoirs and puke everywhere.
There was a big caution in the M&O to reduce pressure to zero below a certain level. 600psi comes to mind. And if I recall, we used to listen for the "clunk" of the shuttle valve when applying pressure.
W1