Game Lags Severely

[Pandalus]

Hello,

I am hoping someone can help me figure out if the reason for KSP1 lagging on my laptop is an issue with the laptop, with the game, or both.  

My son and I have been playing KSP1 on my Lenovo for a couple years now and have had no issues.  Recently I was running a training lesson with my daughter and the game seemed to work fine.  But when my son started playing his saved game the game lagged severely.  I tried one of my saved games, same problem.  I later tried the Getting to Orbit training lesson and it started out fine but about half way to orbit the game started to lag there, too.  About 4 seconds of real life would go by for every 1 second of game time.  But, I switched to the map screen and the game would speed back up to normal speed.  Switch back to... whatever mode it's called when you can see the rocket and it would slow back down.  Map mode - fine. I also noticed the game clock would flash green and yellow several times but remain on green in map mode.  Yellow in the other mode.  Not sure what that means.

I made sure I was upgraded to the most recent version (version 3190, 1.12.5 Windows 64x)  tried cleaning up my hard drive,  tried turning on silent mode and not running background tasks with my North anti-virus, tried adjusting the scenery and rendering settings (although I couldn't tell if they stuck because when I would go back to settings they were often restored to what they were before).  None of that seemed to make a difference.  After restarting the game would run at normal speed for a short time, then slow down, at least in the tutorial.  After slowing down, even reverting to the starting screen would be jerky.

One more thing, the game takes two to three times longer to load than it used to.

My laptop is about three years old now.  But I don't seem to be having problems with my other uses, which admittedly is mostly just watching videos online and internet browsing.  

Any help?