Hi thanks, it wasn’t that though. It seems to have stopped giving that error after I installed High Sierra on an external HDD to test to see if the problem persisted. However I installed Fusion 9 Studio on that and it worked fine, so I re-booted to the internal HDD running Sierra and tried the same Planar Track on that. It Worked Fine again!?!? and has continued to work ever since. The only error I get occasionally now is an “out of memory” error which I think occurs because I’m trying to track too many frames at once.
Ive heard that installing later versions of MacOS can sometimes make the computer incompatible with an earlier OS version. I tried re-installing Mavericks and it wouldn’t install saying my MacBook Pro is incompatible. Well it used to be compatible, having run Mavericks on it for years!!!!!
I’ll stick with Sierra now since what has been changed seems to have stopped the Segmentation error problem.
Rangeway Productions