Microsoft has released updates to the October 2013 Cumulative Updates for Lync Phone Edition that have some significant bug fixes. The updates address things such as missing call records when a call is answered and the phone is locked, login issues, and certificate issues. The complete list of fixes may be found in the KB article links below.

Additional Notes:
Lync Server 2010 build number is 4.0.7577.223

Lync 2010 Client build number is 4.0.7577.4409

Lync Server 2013 build number is 5.0.8308.556

Lync 2013 Client build number is 15.0.4535.1510

Lync Group Chat build number is 4.0.7577. 4409

Lync Group Chat Server build number 4.0.7577. 4409

Lync Group Chat Admin build number 4.0.7577. 4409

Lync Attendee build number is 4.0.7577.4356

Lync Attendant build number is 4.0.7577.4098

Lync Phone Editions build number is 4.0.7577.4414 (except CX700)

Lync Phone Edition CX700 build number 4.0.5755.4411

Lync 2010 for iPhone build number 4.7

Lync 2010 for iPad build number 4.7
Lync 2010 for Android build number 4.0.6509.3001

Lync 2013 for Windows Phone build number is 5.2.1072.0

Lync 2013 for iPad build number is 5.2

Lync 2013 for iPhone build number is 5.2

Lync 2013 for Android build number 5.1.0000
Lync Basic 2013 build number is 15.0.4420.1017
Lync VDI 2013 build number is 15.0.4420.1017