Every morning the user login is pretty slow (sometimes I even get a 504 Bad Gateway). The rest of the page (category pages, product pages, ...) is fast, though. After flushing the cache the user login is fast as well. It stays fast for the next 24hrs. Next morning it is slow again until I flushed the cache.
System>Configuration>Advanced>System>Scheduled Backup Settings is turned off (no)
Cron.php is running every 5 minutes. Advanced>System>Cron is set to the standard times.
System > Configuration > Advanced > System > Log Cleaning is set to yes
I'm also deleting sessions which are older than 7 days every night. Obviously I considered this to be the issue but I turned it off and the problem was still there the next day
I only have third party extensions from Mirasvit (Spinxh Search) and Amasty (Checkout, customer attributes and shipping restriction).
Theme is Ultimo.
Magento is 126.96.36.199
Any idea what the reason for this strange behavior could be? Any help would be appreciated. Thx