I have a Frigoboat twin bd50
freezer thAt was giving me fits for the year I had the
boat. Ended up with pressure readings like yours, positive and negative. Solution was to pull a vacuum on the system for four hours, then close the gauges and
monitor the pressure for an hour or so. If it remains constant the system is tight. If it moves you have
leaks to resolve. If tight reload with gas and go.
I have not stayed in a holiday inn in a while and have no formal
hvac training. I have read a lot of the
forums, Kollmans book, and paid a lot of attention when a tech did the same thing 8 months the prior. I had been wrestling with my system up until the week of the departure. Ended up deciding to vacuum as described at last minute. Clearly not a decision to be taken lightly. But a good one as the system has been tip top for the 6 weeks since. KOW. Ymmv.
Btw I did have to sort out door seal issues (frost screws the units up) and clean out
salt water strainers and pumps along the way. And having a sight glass made the refill much easier, as well As a warm empty unit. But there is nothing like understanding your own system.
Making ice in the keys