Warranty claim misuse

Baught a ws200 welding machine from Cash Crusaders in Rosettenville on 01-06-2020 they could only test the mma side of the machine and not the tig I was told that if there was a problem I could bring the machine back I had used it for approximately 4 hours on Saturday and Sunday when the machine blew up while on but not in use The following Monday I took the machine to the store and was told that it would take 2 weeks to repair I did not get any feedback concerning the machine so I went to the store today 18-06-2020 They told me it was due to misuse that that the machine blew I ask them how was it misused because it has a built in thermal protect switch and it was not in use when it blew l then wanted to speak to the technician and a written feedback as to why the machine blew his awnser was the pc boards were damaged so I asked him to open the machine and see what was wrong It was not the pc boardthat was damaged but the transistors that he saw was blown So did he or didn't he open the machine for fault finding or was it easier to tell the customer it was misuse to void any claim /warranty