If you’ve ever shot infrared photography, you’ve probably run into hotspots before, and they probably ruined more than a few of your shots.
If you haven’t seen them, a hotspot is a bright spot that forms in the center of the image.
In general, some lenses form hotspots, while some do not. Hotspots will get more intense at smaller apertures, and are usually not present at wider apertures. On some lenses the hotspot is very aggressive and the lens is not usable at any apertures, on some the hotspot is mild and is only present at borderline apertures.
There has been a lot of community efforts to share which lenses work well and which do not. We compiled a comprehensive list of feedback on lens performance, but there is a lot of conflicting reports because even at any given aperture, hotspots only appear in some conditions. So while there was a lot of mixed reports, one thing that seemed clear was that hotspots were a lens specific issue.