I had fingerprint enabled before the Marshmallow update to my S6 and it worked perfectly. Now I'd say it recognizes my fingerprint about 25% of the time, and never on the first try. A trick I'm learning is that once you wake the phone you need to give it about five seconds before it'll "take" the fingerprint. Even then, it still works less than half of the time.
Which is not at all how it worked in Lollipop, which in my opinion was nearly flawless. Is this being looked at? I haven't changed anything since the update.