Ever get the feeling something just isn't right? This think is making me think to much

So i bought a think two weeks ago knowing it needed batteries. would go about 4-7mi on a charge. Drove the kids around the neighborhood a couple times. I put 6 new deka’s in and charged (old silver charger) for 8ish hours. Drove around neighborhood and noticed the electrical leakage warning display came on intermittently while driving. Found out even with new batteries I still only got about 6 mi to the charge, let charge overnight and tried again with same result about 6mi. I was fortunate enough the previous owner gave me NOS factory ford delta q charger and upgraded cluster from EIM. Figured before i go chase things ill install both and go from there. Installed both delta q (7201) with instructions from TSB and new cluster. In the instructions it says do not use yellow cord gfci because it is not compatible, I do not have that one, it is a yellow plug adapter that is a gfci. Well it rips after about 3min of charging. No faults on charger flash just trips gfci. i never had issues with this tripping with old charger so I’m not sure if that is the problem. I let it charge like that a couple of times and got the cart to move forward and backwards but haven’t driven it to see if anything else is askew . I have the service manuals and pinpoint tests so I will be tinkering this weekend just wondering if anyone has seen something similar and can give me some insight. I am going to buy a new gfci switch to double check that but other than that i am going to start with the leakage issue because if there is that is probably what’s tripping gfci. Oh and I didn’t wire the ac plug to cart yet just tried to charge off of factory plug on delta q. Any help or advise would be appriciated