"an issue on" means: "an issue on the topic of" and for that reason can only be used when one can insert the phrase "The subject of" once the "on", though "an issue about" can utilised just before nearly anything. I like pet animals much better than cattle = 'Accurate' https://rotatesites.com/story21411597/hoodies-exporter-in-pakistan-can-be-fun-for-anyone