The folder C:\ProgramData\Symantec\Symantec Endpoint Protection\<Current Version>\Data\CmnClnt\ccSubSDK\ is filling up with thousands of submission files that are all of similar size around 3.85MB.
Clients experiencing this issue all have an application in common:
C:\blp\Wintrv\blpcbbap.exe
{KNOWN_ISSUE.EN_US}
Workaround
Disable Client Submissions under External Settings for affected clients.