I have had this issue since the Server Upgrade
It has happened a few times, ignored it as I was not aware of what forum software changes were being made, but they should all now be completed
The forum loads without any problems
I then click on "Show unread posts since last visits"
Prior to the Server Upgrade this always responded
About two thirds of the time it does not respond
When this happens I then try any other link, for example "Profile", but this also does not respond
I then close the window and try again about 30 minutes later, no problems
Tested on two computers, same internet connection
Windows 10
Chrome 71.0.3578.98
Cache set to delete after window closed 15 minutes
Virgin Media 100MBps, connection typically 42MBps, ping typically 30 to 50ms
I also have noticed this issue although not as frequently as the OP.
I'm using Windows 10 and Microsoft Edge. Opening the forum in a new tab in Edge solves the issue.
FWIW I've been getting this problem occasionally on many sites I visit (including this one, but no more than on any other) using Chrome, but not with Firefox.
I am currently only seeing this issue on this forum
I use a few other forums that operate SMF but have not seen it on any of those
I suspect there is a script still loading, which is preveting the browser from responding (a known issue with Chrome)