Relic shield and up not properly working with ranged auto attacks?

I know this is supposed to be me reporting a bug, but I need clarification as to if anyone else is experiencing this as well.

Relic shield's monster execution effect does not seem to work with champions that have a ranged basic attack that aren't marksmen reliably for some reason. It's intermittent and It's hard to tell when it works and when it doesn't. This bug doesn't seem to effect everyone either. Specific champions such as Thresh. I can't seem to remember who else I had this issue with. Either way, if you guys have experienced this let me know, I'll try to get a video up if need be