[Sergio]

Your voltage readings are not possible to obtain from the cart so You likely had the meter probe on the wrong place.

Make sure the meter negative probe was on the pack negative battery post.

That is the only negative post not connected to another battery, instead it has a cable that goes through the OBC to controller B-.

The symptoms that you describe could be related to a weak cell in a single battery creating an open circuit during load.

Since the cart does run eventually, the OBC lockout may be the culprit since it also prevents the reverse buzzer from making a sound.

You can try unplugging the OBC 6-pin connector and placing a paper clip or stiff wire to jump the White with the Blue wires on the harness side of that 6-pin connector.