I think I know how to reproduce this... Targetting for spells is done as a circle; for single-target spells, it is a circle of zero width (a point). If your character 'footprint' (the circle that shows up under your character when pointing/selecting them) intersects the targeting circle, it works.
Normally characters cannot overlap, so no problem - single-target spells stay single target. But after just climbing up/down a vertical surface, the characters can overlap. Meaning single-target spells can affect several at once.
Invisibility for everyone!
[Evil laugh before running off and testing...]
Last edited by RBarbare; 20/01/21 10:57 PM.