I've got a few pips in an area that ranges from 40C to 78C, so outside the comfort zone for pips, but within the comfort zone for pincha peppers. After wrangling several into the area and building a compactor, I filled the compactor with about a dozen seeds and then deconstructed it.
Area is four tiles high and the tile they are planting into is 14 tiles away from the nearest plant (another pincha pepper farm). They go over to the pile of seeds, a "seed delivered" message will pop up over them, but they never actually put the seed in their mouth.
I'm using ladders to prevent them from planting willynilly, I've opened a half dozen tiles over time though.
Maybe because they have to traverse the area of >70C to get to the area of ~50C that they're trying to plant in, they abandon the whole process as soon as the pathfinding algorithm kicks in? Their body temperature seems fine, one is at 46 and the other is at 68. I've been watching them for over fifty cycles now and they haven't done anything.
Steps to Reproduce
Long room with sandstone, dirt, and copper ceiling, pincha pepper seeds, pips. Ladders from left to right along the ceiling, open space on the right for planting.
This issue has not been confirmed by a developer yet.