The AC out is doing bad contact and I can listen this 'burning' noise when trying to move/press the connector on the equipment. Only pressing the plug in certain direction will keep it making full contact. I've changed the AC output connector (GST18) as the L1 pin was very dark (like bunt/oxidised) and it's almost impossible to clean/sand it. It works for few days and when I've returned from the weekend, no 220v on the system and again, it intermittently provide 220v when I press the plug to the sides (and the rsrsrsrs noise of bad/contact came up again) and looking at the L1 pin of the new connector, it seems already darker than the others (just 3 or 4 days running).
It may be something related to the internal connectors. Can I check the internal AC IN/OUT connectors without teardown the whole inverter?