So I went to add the yeast to my beers and when I opened the first bottle to add, there was a significant hiss and so I poured it into a glass and there was plenty of foam. Thought I had a one-off, so I popped another bottle and again, plenty of carbonation/head. I then put a few in the fridge to drink later (couple hours) and then opened those and not much carbonation. There does appear to be some in solution; but it soon fizzles out leaving a nearly flat beer. I know that CO2 dissolves better at colder temps and not having a huge head of foam on my beers is desirable, but there doesn't appear to be much CO2 at colder temps.
Interestingly, my next batch is doing the same thing (did not use gelatin with this batch). More carbonation at room temperature compared to cold. Both batches have the same caps as well - and none of my other batches have used these caps.
At this time I really don't want to add yeast and recap - afraid of getting some bombs. So, I'll probably just drink these myself and look to not use those caps anymore. The only other time I had trouble with carbonation is with an Irish Red this past winter, but they were bottle conditioning in my garage which was too cold - once I moved them into the house, they carbonated up quickly.