Broken Sunkko 709A?

A few months ago I got my Sunkko 709A spot welder from AliExpress, and it has worked fine- until now. I have only welded a few batteries with it, and suddenly I hear some funny sounds inside the welder. The sound reminded me of something short circuiting, but it lasted a few seconds. I turned the welder off immediately, and tried to turn it on some minutes later. It turned on, and the sound came back. Next time I turned it on, it tripped the circuit breaker.
I have not opened it yet, because I'm waiting for the suppliers answer about the "1 year warranty", and don't want to break the warranty seal. But I don't know the chances that's going to work out...
So, does this sound like a familiar problem? I've read about triacs that stop working, and PCBs going bad. If I don't hear from the supplier I will open it and post some pictures here...
I am grateful for all suggestions and help!

Of course the seller won't help, so I opened the thing.
To me it looks okay in there, but I'm no expert... I took two videos when turning on the welder.
The first one does not trip the circuit breaker, but you can see some things happening under the triac.

https://youtu.be/14KZwfkb5bs

The second one shows that the welder trips the circuit breaker immediately.

https://youtu.be/er41HW6xgFQ

Does anyone know what might be wrong with my 709A welder? Right under the triac there is something going on! Should I replace the triac?

[youtube]14KZwfkb5bs[/youtube]

My new 709A does the same thing as the video above - anyone know what's wrong?

TIA

A piece of shit. Period. I have a dead one too. My seller did send replacement PCB but the repair is more costly than the unit price.

Will sell mine with new parts. $65 plus shipping. All new PCB and parts they sent likely to need replacing. Two welds and blew the circuit.

Can not say whats wrong, but I do know that the triacs blow now and then on these.
Especially on the 110V model.