On the last couple of polycarbonate prints with my Prusa, one or more layers have been completely skipped (i.e. no material extruded). The rest of the print is fine save some minor warping. I'm printing in an enclosure that gets up to ~60 °C with the power supply outside the enclosure. I'm also printing out of a dry box with a fairly long bowden tube. I suspect it has something to do with overheating because this doesn't happen when I print without an enclosure.
I cracked the print in half just to take a look in between the layers.