SQL Server 2014 VSS Error

My SQL Server backups are failing. SQL Server 2014 SP1. OS is Server 2012 R2. 'vssadmin list writers' shows SqlServerWriter with a 'non-retryable error'. After a reboot the writer shows no error but errors out after attempting a backup. I get the following errors in the Application Log:

Log Name: Application
Source: SQLVDI
Date: 7/25/2016 9:38:55 PM
Event ID: 1
Task Category: None
Level: Error
Keywords: Classic
User: N/A
Computer: xxx.xxxxxxx.net
Description:
SQLVDI: Loc=TriggerAbort. Desc=invoked. ErrorCode=(0). Process=1772. Thread=8536. Server. Instance=MSSQLSERVER. VD=Global\{1F124942-8720-4F52-A0C9-21A29D20189E}314_SQLVDIMemoryName_0.
Event Xml:
;


1
2
0
0x80000000000000

2106877
Application
xxx.xxxxxxx.net



TriggerAbort
invoked
0


1772
8536
...