I realize that there is a new advanced(?) plotting function in Prime but some of us are constrained to Express.
In Prime 6 Express, define TT as a range variable for plotting 120 deg F,119 deg F . . 103 deg F.
Plot TT vs TT. get
Plot function against TT, get:
Strange effects we sure may call a bug.
As we know, temperature units can be a beast. In case of your plots, the problem seems not to be where the red error is but its the abscissa - there is only base unit K allowed.
BTW, you won't have these problems with the new "advanced" (nice joke) plot component as it doesn't support units at all.
You are correct, I won't have this problem with the new plotting component:
Well, maybe for 30 days once in a while! But, as Luc has shown there are ways: