I'll put some time into trying to figure it out. I haven't given it much thought, due to never using silicone liners. Navigator, can you post which liners you have used and are using? And denise, which liner did you use?
I have several different liners from different suppliers. My two original liners come from the Upland company, which is no longer in business. I also have one of the "stiffer" kind, from WSP, that doesn't need a box around it, you know the kind I mean, BB has them too. And most recently, I bought one from Nurture Soaps when they had a great sale.
My soaps always look like Irish Lass's on the left, I've never had one that looked like the one on the right. I soap at room temp these days, but I haven't always, and I never had a bubble problem when I didn't. I warm the liner in the oven while I'm soaping. Put it back in the oven after pouring, and turn the oven off, but there are times I've forgotten to turn it off, and only noticed when I went back later to check for gel. If I notice that it's gelled all the way, I take it out of the oven, but there are times when I've had to leave for work, and just left it there, with the oven off. The main oils I use are olive, coconut and palm, I don't usually add castor, but I do use avocado, and sometimes shea. I've made goat's milk, buttermilk, yogurt, coconut milk soaps. I'm trying to think of as many variables as I can, because I figure that those who get bubbles must have something in common, that I don't do, or add, and I'm sure someone out there is smart enough to figure out what it is. I sure hope so, because silicone liners have been nothing but a joy for me.
Also, as I mentioned before, is this a recent phenomenon? I've perused many soap forums over the years, and I don't remember reading anything about this problem until recently. That lead me to think that maybe the newer liners were manufactured differently, but since I recently bought one from Nurture Soaps and had no problems, I guess we can rule that out. Did I just miss this in other forums, or has it been going on all along? It just seems odd to me that over the years, using different molds and different recipes, and always CPOPing, that I've never encountered this problem once!