Large model cracked/split horizontally

I have had a problem where some z-axis stepping inconsistency led to some layers being printed slightly above where they were supposed to be.  As a result, there was practically no adhesion for such layers.  They cracked in that area when I tried to remove them from the plate.  But this was pretty frequent, and it seems unlikely to happen just once in such a large print as the one you were doing.

Hmmm...my extruder temperature is 195 and my bed temperature is 95.  I've heard you aren't supposed to go above 200, so I'm not sure raising the temperature would be right.

However, thinking about temperature got me thinking.  I don't have the case enclosure.  This being a long print (5 hours), it got me to thinking:  I wonder if during that part of the print, for some reason, the temperature dropped (maybe the AC came on, though the printer isn't near any vents).  If I had enclosed the printer, I wonder if that would have prevented this problem.

The case will help, but all the brim does is help stick down low-foot print parts. It doesn't 'prevent warping/cracking'.
What causes warping/cracking is an uneven rate of cooling, or too quick a cooling. Again it comes down to temperature at bond creation.  Adding the brim can help stop parts lifting off the bed, but it doesn't increase their tensile strength any as they will still cool unevenly in an open enclosure. Keeping it stuck down may reduce the visual defects of warping and may help prevent catastrophic warping - but all it does is increase the footprint of part to bed, nothing more...

So yes, to the OP, definitely try a case, and also upping the temp to 197-198... a few degrees can and does make all the difference.

ah - okay - so when you said "increase the temperature" you meant even a few degrees.  I wasn't thinking 2-3 degrees would matter much.  Okay, I'll keep that in mind.  I have a crude cardboard enclosure I've made, but I don't use it, as I get a bit anxious about putting a cardboard piece over a heating element that is nearly 200 celcius.  I guess one thing I could do is go buy some sheet metal and cut it to size.

I had this same exact problem yesterday.

I print at 200 for extruder temp and 95 for bed temp with a very well enclosed case on glass with hairspray and with a substantial brim.  I did 4 perimeters and 30% infill on a fairly large object.

It still had several "cracks" in it (but only on one side.  the other side was flawless), and after acetoning it (hoping that would melt them together), they became even more pronounced.  My only guess is that my plastic is bad, mainly because I've had problems with this spool before.  Beyond that, thought, I'm out of ideas.

The plastic was purchased on Amazon from Octave.  I have 7 spools from Octave and this spool is that only one that has given me trouble.  I double that it is air bubbles, though, because the cracks occur at very specific points on the model that are almost exactly the same place on the model (Might be a bad slice or something).  I will take some pictures of it this afternoon and show you what I mean.

Also, be careful printing 0.1mm with a low infill percentage.  I learned that you need ~50% or more infill on certain 0.1mm models in order for the top layer to be solid.  This mainly applies to models that have very slightly sloping areas.