I moved your post to a new thread to keep the discussion better organized.
Unfortunately, the boards in your picture are not ours. You can see on the product page for our dual MC33926 carriers that the silkscreen labels on the bottom side of the board are different. That makes it hard for us to say what might have gone wrong, but if there is a short between VIN and GND on your boards, then I do not expect that to be repairable or something you can work around.
It seems like the current draw from your motors was more than what your boards could handle, so I suggest switching to an altogether more powerful motor driver that is more appropriate for your motors. Our VNH5019 carrier or one of our G2 High-Power Motor Drivers might work, but if you want to be certain you can post a datasheet or product page link for your motors and I will let you know if any of our drivers seem appropriate. To make sure you get our boards you can order them directly on our website or you can order from one of our authorized distributors.
By the way, MC33926 drviers are not intended to be paralleled, so that also might have contributed to your boards being damaged. For future reference, any of our drivers that are intended to be paralleled (such as our dual VNH5019 shield) will have something specifically mentioning that capability on the product page, and if you ever are not sure you are welcome to make a forum post or send us an email to email@example.com asking.