Cider or Vinegar

My fifteen gallons of apple juice, from the mammoth juicing session, was split into two five gallon bins and the rest put in either Demi-johns as wine or bottled and frozen. The demi-johns are bubbling away as wine in the making. The juice that was bottled is in the freezer. The odd bottle that just went in the fridge for immediate consumption has started building up pressure. That's a clue it is starting ferment. I am getting through it. It taste sharp and fruity with a slight fizz.

The juice in the big bins is a tail of two pressings. Both bins had their lids put on and the air locks fitted at the same time. Both bins were put into the cool shed. Nothing seemed to be happening judging by the water level in the air locks. After a couple of weeks I snapped open the lids to see what was going on. One bin had a nice froth on the surface of the juice. Upon tasting it tasted like cider. The other bin had a gelatinous scum on the surface of the juice which I fished out. There was also an acidic aroma. Upon tasting there was a hint of acid. Is this going to be another vat of vinegar? After a little negotiation with H the bins were allowed indoors into the corner of the dining room. I left the bins for a week to warm up to room temperature. That corner of the room hovers around 64 degrees C. The cider bin picked up and start fizzing more vigorously. The vinegar bin just sulked. I thought I have nothing to lose, I mean who needs another five gallons of weak cider vinegar? I made up a whole sachet of general purpose yeast in warm water and got it started. Then I poured the activated yeast into the vinegar bin, refitted the lid and airlock and retired to a safe distance. It was a difficult two days to keep my nose out of the bin. I checked the airlock but no movement. On the evening of the third day after dosing the vinegar I had a test. The juice smalls fruity rather than acidic and you can see the gas bubbles fizzing to the surface. The juice tastes like cider but different to the other bin.

Following my highly scientific experiment I have come to the following conclusions:
a. The lids on the bins are not air tight.
b. The type of apples that are made into juice have different properties.
c. Relying on the apples to provide the right sort of yeast might not be a resilient plan.
d. The temperature of the shed is not right for cider making. It needs to be colder as in the fridge or hotter as in the dining room.