Random Kernel Panics with Shutdown Cause: -64
From the details you provided. It sounds as if the kernel panic is due to to an issue in the firmware of your device. There are two things you can do:

(before doing any of the solutions, always have a backup of your files, especially the important ones) 


Use the App Store to see if there is an update for your firmware. Just and fyi, you should update your system to the most recent version available.
Do a quick Google search on the firmware updates for your model. Download and install.


Worst case scenario: the motherboard could be failing. The apple diagnostic does not always give an accurate test if the hardware. The more in depth apple test is available to Apple Care repair services. 

Best case scenario: all you have to do is SMC reset and a NVRAM reset.

Follow instructions for these resets here:


NVRAM reset
SMC reset


If none of these options work, I would write down the panic error that is displayed in the text, and do a quick Google search for anything related to the panic error, i.e. why does (put panic error here) occur....