Fake sim800L modules

Hi I’m from India and I’ve finished R&D using sim800L breakout board for a production project. One peculiar thing I’ve noticed is some of the modules don’t even power and some of them power on but no response using the UART.

So i tried reflowing the breakout board with sim800l and automatically some of them started working. So i was suspecting dry solder. Also some of their stickers melted during the redlow and some of the stickers maintained after the reflow.

Can anyone suggest me the authorised dealer from where to buy sim800L breakout board or even the module itself , I can design and assemble them on my own. I’ve tried robu, robocraze, electronics comp , all these Indian websites, every time i order 10 qty 5 or 6 work.

Your help will be greatly appreciated.

Note: the power related problems are all sorted no problem in connecting to the network , I’ve used rated supply and other things such as cap placement, etc. It’s only that some of the modules work and some dont.