The problem shots are slightly backlit, but mainly lit by what appears to be open sky.
The better shot appears to be lighted by diffused sunlight from the front.
Those two light sources have really different character and colour.
That being said, I would think that there may be some scanning issues involved as well.
Hi Matt, these were all scanned at the same time on the same strip! literally at the same time, open lid put in film and scan. open lid remove film. Anyway, not to worry, I have been doing some meter tests Vs my D700 and Minolta IV. It appears that centre weighting is pretty accurate, in fact more accurate than the D700! Plus my manual lens has a CPU chip so I can also use Matrix metering if I want. So no need for me to worry. I will run a few more rolls with these settings before I decide. Thanks Paul