I have some additional information:
- For the dedicated pools, the error log shows the username (e.g., Sessions for user DOMAIN\user timed out)
- For floating, non-persistent linked clone pools, it shoulds the Active Directory SID of the user (e.g., Session for user S-1-5-21-467163239-218728984-193154552-17047 timed out)
- I still haven't figure out when it says Session for user null timed out.
Any ideas of what this could be?