Shore Power Problems

(Greece)

I own a boat bought from the US (110V) and transported via container to Greece (220V) where I reside. It has two shore AC input lines (30amp each) and a generator. The source selection switch is a Kraus-Naimer C42-C17591 3 position switch (Line 1 - Line 1&2 - Gen. )

I wanted to retain the original 110VAC configuration, so I used a 220 to 110V transformer (Seven Star ATVR8000) before the main AC selection switch. All the connections were made by an experienced electrician.

When I use the generator as my 110VAC source everything works perfectly. When I use either the 1st or both shore power lines something goes wrong. Most of the times the dock's power center anti-electric shock breaker "drops". The dock power center terminal has an installed anti-electric shock breaker for safety reasons which cannot be removed by any means. Two or three times for an unknown reason the breaker didn't "drop" and I noticed that some electrical appliances from the 1st AC panel (eg water heater, air condition) worked while others didn't (eg Microwave oven, all the inside wall-plugs). Nothing from the 2nd AC panel ever worked, because when I try to switch on the main 2nd AC panel switch, it "drops" automatically.

The shore line power worked fine in the US, but I found out that the dock power center there, didn't have anti-electric shock breaker installed. The 220 to 110VAC transformer works fine when I connect it directly to a 110Vac device (eg a fan). The transformer's breaker never "dropped". The cable connections to the main ac selection switch were checked, confirmed and are correct.

I also tried a different dock power terminal, but the same problem insisted. Could the problem be a minor electric leak somewhere in the system, which the generator is able to overcome while the dock power center cannot, and if that's true how can I locate and fix this problem? The ground bus terminal is connected with the DC bonding system and there is a galvanic isolator/zinc saver somewhere in the ground wire system.

The electrician also tried uninstalling the galvanic isolator and tested the system without connecting the green AC ground wire but nothing changed (again the dock's anti electric shock breaker "dropped").
We have tried numerous other tests but didn't accomplish anything. We cannot locate the problem so any help or suggestions would be welcome.
Thank you in advance.