Very strange! I’ve tried targeting by clicking on the player frame, tried clicking on them, tried reloading ui, tried un-toggling any auto-selfcast options. I also don’t use any macros but it could be interference from an addon? I’ve found only a few instances of this occurring for other people but it does seem to be an issue that’s popped up in BFA specifically. At the moment, I’m completely unable to Soulstone other people in my parties/raids!
I FOUND IT! To anyone who has had this peculiar issue happen-check your addons, specifically bartender4. After testing out casting Soulstone on a party member disabling all and slowly turning them back on, bartender4 proved to be the culprit. It could be a conflict with another addon I have running since there is no mention of this issue on bartender’s Curseforge page but their Main file hasn’t been updated for some time.