RSS Feed Not Updating
 

My only RSS feed stopped working a few weeks ago and I'm uncertain why.

Feed source: http://www.opentrackers.net/rss/lastChanges.php (appears to be a valid feed based on validator.w3.org/feed/)

Manually executing "Run Scheduled Task Now" from within the RSS Feed Manager appears to run, but the "Last Checked" field remains empty even though I verified the feed was updated recently. Manually executing "Run Now" for the RSS Poster Robot scheduled task also appears to run, but the scheduled task log shows no entry for the robot (verified the task was set to log).

I'm running 3.8.4 PL2 with about 150 active users at any given time. Any suggestions for troubleshooting this? The only thing I haven't tried is deleting the feed and recreating it.