Nightshade said:
Yea wayright is correct they aren't self incompatible some can be sterile but they can self pollinate.
Self-incompatibility issue doesn't mean they won't self. The reason some are sterile is because it has a self-incompatibility issue. If I'm wrong, then cross pollinating genetically different c. flexuosums shouldn't show fruits setting more. Capsicum evolved from being completely self-incompatible. It could be a throwback or an older capsicum species.
Edit:
I don't know if this will be helpful.
"Attempts to increase the first germplasm samples of C. flexuosum under greenhouse conditions suffered from poor seed set (Paul Bosland), likely caused by self incompatibility, suggesting the need for larger samples of germplasm."
"The plant below produced a large amount of flowers but without any fruit set. Even manual pollination with the plant's pollen did not resulted in any fruit set, but after cross-pollination with another C.flexuosum it managed to set fruit."
Both quotes are from
http://wildchilli.eu/c-flexuosum . I'd like to reproduce the cross-pollinating experiment with genetically different c. flexuosums.
Here is another source:
"Most Capsicum species have flowers that are complete and are self-compatible. Self-incompatibility is found in the wild species C. cardenasii, C. buforum, C. Flexuosum, and some accessions of C. pubescens."
Link to source (Flower Breeding and Genetics: Issues, Challenges and Opportunities for the 21st Century)
Edit again:
I think c. flexuosum is partially self-incompatible. Perhaps it's not accurate at recognizing self-pollen. There are degrees of SI.