Recently, muy phone has had several instances of instant battery level drop; not as in quick drain, but rather, immediate drop. I've been able to document these two occurrences :
Between the first and second occurrence, I uninstalled apps that were using data on the background (such as games and whatnot), I monitored the battery usage per application, disabled unused applications, and used motorola's app battery optimization. And while doing all that did in fact improved my overall battery life, that didn't prevent it from "spontaneously" dropping to near 0%.
Also, I noticed that in both cases, there was a slight increment in battery level, before dying (It was charging but I had to unplug it to attend a call).
Finally, there was no significant phone or battery heating that I could perceive.
Another sympton, although I'm unsure this is related in any way, is that my phone turned off, as if battery completely depleted, while having battery level at 15:
I've tried wiping my cache partition, and hasn't occurred since; however, I think that this might be purely coincidental.
My phone information:
I have not been able to find this question repeated here on SE.
Any further needed information I can provide, please ask.