But have you tested all of the permutations of the three main phase wires with the bullet connectors? Without using any of the five wire connector at all? Does it just hesitate under load or also when running with no load at all? I don't think it is your throttle if you looked at the connection. With enough load, your voltage on that small battery could diminish to the point where the bms in the battery would shut down, to protect the battery. That probably shouldn't happen though, if the battery is fully charged, and balanced. A balance problem in the battery could shut the battery down, if one cell went too low, under load. It does seem from what you say that it sounds like the phases are hooked up right. Not sure what else to suggest other than finding someone on endless-sphere who could help you, from your area, or someone with an ebike tester gadget.