I did more extensive testing on my bard and I am still seeing some issues:
My bard is a level 17 dwarven bard with a 16 cha wearing full plate:
I tested the following spells at the following frequencies in the tent in the MC and had these results:
Mage armor: tested 5+ times none failed
Cure light wounds: 5+ tested none failed
Removed fear: at least one failed
Protection from alignment: at least one failed
Amplify: 5+ tested none failed
Bulls strength: at least one failed
Cats grace: at least one failed
Cure Moderate: at least one failed
sonic weapon" 5+ tested none failed
Eagles splendor: at least one failed
All level 3s failed at least once they included:
Haste
Cure serious
Wounding whispers
Good Hope
I had no reason to test spells 4+ and based on my understanding of the feat cantrips should still be subject to spell failure as well.