Q: El Capitan requires replugging thunderbolt to computer

After I upgraded to el Capitan, each time the computer goes to sleep the connection to the thunderbolt is turned off. In order to have the double display I have to unplug and plug again the Thunderbolt to the computer.  This hadn't happened ever before. It also seems that if the computer has been asleep for a very short while, it might recognize the Thunderbolt and reconnect by itself in a random fashion...

El Capitan also seems to have slowed down all of the program openings in the computer and I had issues with Outlook (resolved after installing an update)

Any updates to make it work like it should? An update is supposed to improve the computer behavior, not degrade it....