Check for update doesn't work properly

Dears,

I've rolled back to Spark 2.8.1 and tried to use "Check for update" function - first time it said "No updates" (even though 2.8.2 is already issued); any subsequent requests didn't bring even that message.

After restart tried to reproduce - it generates mess "not updates vailable" all the time during certain period, but then stop checking for updates again.

Regards, Roman