Here's what I've observed since my last post. As mentioned, the app is no longer crashing since the update. That in and of itself is a big improvement. However, like others, it still does not notify me of new voicemail messages most of the time. I still have to manually check. Also, periodically, I'll open the app, and it opens with an authentication failed error. If I exit out of the app and go back in, it usually works the second or third time. So, still seeing a few issues with it, but it not crashing is still better than what it was doing. At least I can get the voicemails through the app now.
Not an optimum solution, but I have found that if I maximize the tile, the notifications will appear. Mid size tile seems to come and go, and the smallest tile never seems to work. I am using standard voice mail.
I have no problems of my voicemail indicator. It always shows up on my lock screen and my live tile showing phone niumber when using wide tile, if using medium tile size it will show a voicemail number. If in small tile it will still show a number. So love this samsung ativ s neo wp 8.1 and can't wait upgrade to Windows 10 Mobile this October.