Bug between Tahm Kench and Taric
If Taric uses his ult, while the the invincibility is up Tahm can't stack his passive on anyone effected by the ult.
Last night I was playing as Tahm with Ezreal for my ADC against a Taric and Jhin when this first happened and it happened every other time I used my Q or autos on an enemy champ while effected by the ult.