When the curviness is at the minimum, blank spaces appeared on Rs.
Concerns :
cap : R
smallcap : R

When the slant is at 30 (maximum), we just loose the Z glyphs (lowercase et uppercase), and the small B is black on top counterpoint.
Concerns :
low : z
cap : Z
smallcap : B

When the thickness is at the minimum (4) some glyphs are deformed.
Concerns :
cap : S
smallcap : S

When the Xheight is at the minimum, some letters are deformed.
Concerns : low : a-c-e-k-s-y
: cap : G-S
: smallcap : G-J-K-P-R-S

When the contrast is it the max, some blank spaces appeared in the R and the Z.
Concerns :
cap : R-Z
smallcap : R

When the thickness is a the top, the Q cap tail got an other wrong angle.
Concerns :
cap : Q

Serif width : 98
serif height : 100
serif terminal : 100

Here, problem with the serif terminal.

When the contrast is at his minimum (-1,30), some glyphs are deformed ou have some weird weight repartition. They is also some crossing strokes.
Concerns :
low : w
cap : A-M-N-V-W
smallcap : A-G-M-N-S-V-W
numerals : 4-5

When the width is at the maximum, some letters have bugs. Some have not sufficient thickness, or the components are crossing.
Concerns :
low : v-w-y-z
cap : A
numerals : 1-5

Serif width : 96,21
serif height : 100
bracket curve : 100
serif arc : 0,60

The number 7 has a problem. The bottom going up with the serif arc parameter.

The top of the t should should not be affected by the ascender parameters.
see byte-foundry/prototypo#296

Problem de Q tail, when the thickness is at the minimum, the angle is not the same.
Concerns :
cap : Q

When the extremity contrast is at his maximum (-0,20), some glyphs are deformed, or partially affected by the slider.
Concerns :
low : z
cap : D-M-Z
smallcap : D-M-Z

Serif width : 96,21
serif height : 100
bracket curve : 100

the lowercase x is completely blocked at his top.

Serif width : 96,21
serif height : 100
bracket curve : 100
serif arc : 0,60

The capital K has a serif who jumps to the infinity.

only on generated typeface:

tmp workaround with #5401dfe9c142b6897f7ce0de40791996e9455552

We only have serifs on the external side of the curve. it concerns SCJGsc letters

When the thickness is at the maximum, some glyphs are deformed, they are often too closed, or the counterpoints become to small.
Concerns :
cap : G
low : e-s-x
smallcap : G-S

When the Xheight is at the maximum, some letters are deformed.
Concerns :
cap : G
smallcap : G
numerals : 5-6-9

When the curviness is at the maximum, the e low and the numeral 2 get some blank spaces, between the strokes.
Concerns :
low : e
numeral : 2

an are not wide enough. y is not affected by width at all.

When the aperture is a the minimum (0,30), Some letter have a lack of curve.
Concerns :
cap : S
smallcap : C-G-S

When the Extremity contrast is at the minimum (-1,50) (without the general contrast) contrast make some bugs on certain glyphs.
Concerns :
low : z
cap : D-K-N-V-W-Z
smallcap : D-G-K-N-V-W-Z

When the aperture is at the maximum, the lowercase "g" become weird.

When the crossbar parameter is at the minimum, some glyphs are deformed.
Concerns :
cap : B
smallcap : B

When the curviness is at the minimum, there is some serifs conflicts on the Ss.
Concerns :
low : s
cap : S

When the capital height is at the minimum some glyphs deformed.
Concerns :
cap : G-S-Y
smallcap : G-S-Y

When the thickness is at the minimum (4), the two diacritics (ij) do not follow the value. They stay a bit bold.

When the width is at the minimum, some letter are deformed.
Concerns :
low : c-e
cap : C-G
smallcap : C-G
numeral : 5

The spacing is affected on severals letters, when the width is used.
Concerns :
low : f-j-e

When the parameter Slant is at 15, there's some bug, in terms of spacing and missing glyph, and also serifs problems.
Concerns :
numerals : 2(missing)-9(spacing)
smallcap : Z

Serif width : 96,21
serif height : 100
bracket curve : 100

the Ss have a problem with the serifs.