STK - 0050 Power pack short - Repair Fail

Hello everyone.
I went ahead and tried to repair the metz mecasound ax 4960 which had the right channel's power pack low side pnps shorted. I removed the old one and tested if the previous stage- vas transistors were short but they where testing good. I changed the power pack with the new one and first tested the amplifier with my bench power supplies by applying voltage straight into the bridge rectifier so i can have current limiting but i had no overcurrents and the out put signal was fine. But when i plugged the amp into power and the dc protection relay closed, the low side of the power pack got shorted the same way as before. The amp has no bias and dc offset adj so these cant mess up the output stage. What could be the issue here.
I dont think i will buy another power pack for 15 euros again to replace it and mess it again but i posting because i am curious what could cause this.
Best regards
Found the problem... The pack is counterfeit. I also moved the working pack from the left to the right channel and it is working flawlessly. Do you think i should use the descrete option because all the local stores seem to sell the same pack. I really dont want to throw away this old amp.
Thank you