We host SmarterTrack on Windows Server 2016 running IIS-10.  We're running version 14.1.6885.28379  of the software

For the past few months we've seen repeated errors like below occurring every 5 minutes.  Any indication on what could be triggering this and how to stop it?

Event code: 4005
Event message: Forms authentication failed for the request. Reason: The ticket supplied was invalid.
Event time: 12/13/2018 1:03:46 PM
Event time (UTC): 12/13/2018 6:03:46 PM
Event ID: 9fdebc853f3645f18bf7238f9954a9c1
Event sequence: 4095
Event occurrence: 757
Event detail code: 50201
 
Application information:
    Application domain: /LM/W3SVC/4/ROOT-1-131891312613374198
    Trust level: Full
    Application Virtual Path: /
    Application Path: D:\LIVE\[redacted]\SmarterTrack\
    Machine name: [redacted]
 
Process information:
    Process ID: 752
    Process name: w3wp.exe
    Account name: NT AUTHORITY\NETWORK SERVICE
 
Request information:
    Request URL: [redacted]:443/api/Chat/CheckIsSoundEnabled/39
    Request path: /api/Chat/CheckIsSoundEnabled/39
    User host address: [redacted - public IP of requesting user]
    User:  
    Is authenticated: False
    Authentication Type:  
    Thread account name: NT AUTHORITY\NETWORK SERVICE
 
Name to authenticate:  
 
Custom event details: