Slant vs. Cursify

In Filter > Transformation (G 2.6.7) there are two possibilities to slant a font: Slant and cursify.
Why is it that I get different results for one letter in one font, but identical results in another? Is there a hidden check mark somewhere, a setting that influences this?
(If I copy the letter[s] from the non-working file into the working one, it works. So it must be the glyphs file …)
hope you know what I mean!? Greeetz!

The cursify function relies on stem values defined in the master. It should complain if they are missing. So by slightly changing the stem values, you can tune the amount of cursifying.

Ah, okay! I have now (re)entered them and it works! THANKS!