Hi @frankderuyck,
I would compare the outcomes of the first use case on something else than p-values, due to multicollinearity in mixture designs.
Again, without any dataset to test, it's difficult to help you since we have only a partial view at this comparison.
For the first use case, if the model are set up correctly and in the same way between JMP 17 and 18, try to look at the Parameter estimates (and standard deviations), at metrics focussed on predictivity and optimization (like RMSE) and residuals/diagnostic plots.
Since you mentioned the Profiler has similar results between versions, I would guess that the differences you are seeing are mostly due to the use of Mixture designs instead of a calculation change between versions.
Victor GUILLER
"It is not unusual for a well-designed experiment to analyze itself" (Box, Hunter and Hunter)