I've got a HP ZBook with 32 Gigs of Ram that until recently was running Windows 7 and Media Composer 8.3, using a AJA T-Tap via Thunderbolt 2 to output to SDI for a News application.  It operated flawlessly for 2 years.  We just updated to Windows 10 and MC 2018.4 and it's been nothing but trouble.  Yesterday I got the beachball 7 times and had to reboot the system each time.  It seems to really have trouble when I click the Hardware Switch to activate the T-Tap. It also seems to have a problem when dragging through a 30 minute source sequence looking for a shot.  I'm using P2 media on either SD or Fullsize P2 cards in a 1080 project and now have to consolidate my media because cutting off the cards is now unstable and causes crashes.  We have 4 or 5 machines with the same basic setup amd most are having the same kinds of prolems.