4 Battleborn batteries, multiplus breaker tripping. Earth ground adapter?

Hi, my Airstream has a multiplus, 4 battleborn 100ah batteries all professionally installed. When plugged into a gfci outlet my breaker pops on the shore side. Was told due to chassis ground in inverter. Was able to briefly charge using 3 to 2 prong adapter. Wanted to know if there were any dangers to using this adapter? Was working for me

the Multiplus I or II does not work well when plugged into a GFI outlet.
this has been discussed many times on the airstream forum

Victron needs to reply as to why

I’m getting a good charge with this adapter. Just concerned about leaving it plugged in and charging while in storage