Some new updates have been released for Lync Phone Edition devices and this update specifically address the issue where the phone and Exchange were never in sync. When voicemail was listened to on a LPE device 9 out of ten times it was not reflected within Exchange and thus the MWI lamp remained on and a logout/in of the phone was the only way to clear it. This was not a problem in the past but at some point I suspect the issue was introduced in a CU.
The Tanjay (CX700) devices receive the update as well as the Aries (Aastra, HP, and Polycom) - the update process is no different from before with an Import-CsDeviceUpdate command. Alternatively you can use the PS command that Dave Howe created to automate the process for you. The PS1 can be found here - just rename from .txt to .ps1 and run from a Lync Management Shell.
As a complete side not, I currently use MangBlog for my blog postings and a recent update fixed a few things and broke a few others - hence the table formatting...I hope to have the issue resolved soon or perhaps I will move to a new platform (it must run under Adobe ColdFusion)...
Lync Phone Edition for Aastra 6721ip and Aastra 6725ip
Lync Phone Edition for HP 4110 and HP 4120
Lync Phone Edition for Polycom CX500, Polycom CX600 and Polycom CX3000
Lync Phone Edition for Polycom CX700 and LG-Nortel IP Phone 8540
Lync Server 2010 build number is 4.0.7577.216
Lync 2010 Client build number is 4.0.7577.4378
Lync Server 2013 build number is 5.0.8308.291
Lync 2013 Client build number is 15.0.4454.1506
Lync Group Chat build number is 4.0.7577.4102
Lync Group Chat Server build number 4.0.7577.4778
Lync Group Chat Admin build number 4.0.7577.4102
Lync Attendee build number is 4.0.7577.4356
Lync Attendant build number is 4.0.7577.4098
Lync Phone Editions build number is 4.0.7577.4387
Lync 2010 for iPhone build number 4.7
Lync 2010 for iPad build number 4.7
Lync 2013 for Windows Phone build number is 5.0.8250.0
Lync 2013 for iPad build number is 5.0
Lync 2013 for iPhone build number is 5.0
Lync Basic 2013 build number is 15.0.4420.1017
Lync VDI 2013 build number is 15.0.4420.1017