Contrast Preset malfunctions if above a threshold (50%?) value

What is your operating system?
Ubuntu Linux 18.04 (Kubuntu flavor) AMD64

What is your Shotcut version (see Help > About Shotcut)? Is it 32-bit?
21.02.27 64-bit
also
Shotcut-181118.glibc2.14-x86_64.AppImage
and
Shotcut 201128 linux-x86_64.AppImage

Can you repeat the problem? If so, what are the steps?

Repeatable.

If a Preset is added to the Contrast filter with a value above 50%, when the Preset is recalled, an image like this…
Screenshot_20210321_020012

…becomes this…

Screenshot_20210321_015823

Also, after recalling the filter, when the time is advanced by as little as one frame, the indicated value jumps from the preset value to “100%”, although the image display is not the same as appears when 100% contrast is set manually.

Other filters , and their presets, function normally.

Presets for Contrast appear to function properly if the value is less than 50%

A demo video is available.

On 20.09.27 osx the bug exists even for values below 50%.

I only discovered a Preset that appeared normally while making the second cut (shown above; the first cut recorded the wrong monitor), so the “below 50%” was a guess I made on-the-fly as I observed “some work, some do not” for the first time, based upon the Default for Contrast being 50%.

This is fixed for the next version 21.04