Driving around in the rain, using ACC and the near Gap setting (I always use this setting) I had traffic slowed/stopped in front of me and the ACC wasn't stopping in time and the 6 red light front collision alert activated and appeared on the windshield. I had my foot hovering over the brake and I immediately hit the regen paddle and the brake, slowed and all was good. Here ACC didn't work as it should and I think the rain was a factor.
So I decided to change the Gap setting to medium and it worked like a charm, keeping a better distance in the conditions I was in, giving it more time and space to work in a better, more comfortable fashion. A little while later, as I was approaching an area that had some light fog and I then got the "Adaptive Cruise Control Temporarily Unavailable". I tried a few times to re-engage it over the next 10 minutes with no success. I think the conditions, rain with some light fog, caused the ACC to become unavailable. Pretty amazing engineering if that's the case, recognizing that the conditions weren't right for it to work in a reliable fashion so it turns itself off. I'm not sure of course, just my observations and speculation.
I do like the Gap setting change for the situation I was in, I will go back to near once we return to normal So Cal weather as the near setting works well generally. Thought I'd pass these thoughts along and get others insights as well.