When I was rooting in bins, I left for a weekend. I was unable to vent my bins. I was leaving my bins closed for the entire time since then with absolutely no problems. I would open them once or twice a day, fan the bins to exchange the air and close again until next time.
Since that time I have lost 30% of my cuttings and the ones I didn't were only saved because I pinched off the mold and leaves that were turning to mush. This is why they are forming branches so low. I would have lost the cutting if not for doing this. The moisture in the containers are near or at 100% and I know that most would vent but I had zero problems until 6weeks ago.
I also tried using peat pots for transplanting. At that same point I started using peat pots inside cups to ease transplanting from plastic 16 oz cups to 1 gal pots.
Ever since then, I have nothing but problems. I spray the tops of cuttings constantly with Physan 20 to stop or inhibit mold.
These 2 factors, missed weekend and addition of peat pots, led to an almost complete loss. So far I have saved at least half. Most of the other half have failed completely and the other half are on life support.
Oh well, live and learn!