Might be water damage from the button side, my friend had a similar-ish problem, didn't cost anything under warranty though - service center is your best bet.
following with JJEgan, this is clearly a question ([Q]), so you should post it in the Q/A section, you should probably make a thread there next time
Phone: Samsung Galaxy Note 3 (4G-LTE | N9005) @ 2.3Ghz - Jet Black
Memory: 32GB with 16GB Ext-Memory
ROM: Unrooted Stock (UAE-Qatar ROM)
TouchWiz: TouchWiz UX - Android JB (4.3)
Phone: Samsung Galaxy S3 I-9300 @ 1.4Ghz
Memory: 16GB with 16GB Ext-Memory
ROM: Stock BTU (4.1.2 - rooted)
Phone: Samsung Galaxy SL I9003 RETIRED
I might NOT answer to questions asking for help by PM.