One of the downsides to the M201 is the ease with which e-liquid drains into the battery and causes it to start cutting out. A regular blow job and cleaning out with a rolled corner of a tissue, the atty and the charger should get the same treatment, plus approx' horizontal vaping and storage, usually keeps it going without any vapus interuptus.
But, I had one of my 3 batteries-in-rotation, go into cut-out mode yesterday, something they never do, even when chain vaping. Other symptoms were: Atty getting hotter than usual and the draw harder than usual. Did my clean out thing with a tissue and blow job but it still cut out. I checked it out closely with an illuminated magnifier and found it still dirty with e-liquid gunk in places that the tissue can't reach and stuck to this, lint from spare batts being carried in my pocket clogging the side holes.
Solution: Used a nail brush on the face of the battery and pushed the bristles through the side holes. Easy draw now, cooler atty and no more cut-outs...... sorted.
PS: First tried to use a steel sowing pin to ungunk the batt....... don't! Unless you want really hot fingers.