Hi, have a BT SWE 120 STACKER (IN SILVER, NOT ORANGE)

Was working fine but now when i connect charger (Hawker) it flashes orange to start for a few seconds then green for a split second then red and because of that it wont charge. All seems to be ok as it gets very little use but not sure what to test (or how to test it)
Thought it initially may have been the charger but now perhaps it could be shorting somewhere?

Thanks,