they were both at the same temperature (both batches had been out at room temperature all day), and it definitely didn't break down and start curdling. Just got very very soft. It was strange lol. I use SMBC quite a bit and don't find that to be too soft, but the resulting mixture was just gooey.
I put the leftovers in the fridge and pulled it out this morning though. After it came to room temperature again it was still soft, but not as soft as it was the day I combined them. Absolutely a different change in texture from the first day! I had my oven going for several hours and my hands were warmer than usual with all the work I was doing that day. I normally have deadly cold hands haha :p. So I suppose the problem could have been all the heat going on that day... though it still puzzles me that my SMBC was fine until I combined it with the ABC.
Appreciate the help and advice though! I will try combining again in the future (on a day when its cooler in here) and see how it works out!