Downloading certain apps on CM 12.1/13 causes it to bootloop
In my case (Nexus 4 (Mako)), I have it running only on CM 10. WhatsApp then started to cause the boot loop on CM >= 11. Since I need a custom ROM for 4.4+/KitKat or up, I ended up in flashing LineageOS 14.1 (Nougat) and so far it's been working fine for me. (ツ)