iPhone 6 selects different voicemail than touched

When I select a voicemail, it sometimes turns grey, and a voicemail one or two above becomes selected. Screen will also sometimes (infrequently) oscillate between half height and full height 5 or 6 times quickly. This is after an IOS10 update. Phone has an Otterbox case. The home button film from the case has deteriorated and left stickiness around the home button, which I cleaned off. Button seems to actuate ok.

Apple replaced the phone under AppleCare but I doubt this is the only phone that has seen this problem. All other apps seem to work fine.

Could this be a problem with the home button? Or something else? Not sure what would cause that behavior for voicemail.