S6 edge marshmallow upgrade: Fingerprint unlock randomly won't work sometimes?

[AC Question]

Upgraded to marshmallow 3 days ago. T-mobile. Galaxy s6 edge.

My fingerprint unlock won't work about twice per day randomly and i'm forced to input my backup password. Then it works perfectly fine again.

Also, when first plug it in to charge, it will also not work the first time I try to unlock it with my fingerprint and i'm forced to use my backup password.

Things I've tried: restarting phone. Deleting fingerprints and adding fingerprints back. Clearing cache with built in smart manager app.

Thoughts/Ideas?

Thanks