What is your operating system?
What is your Shotcut version (see Help > About Shotcut)? Is it 32-bit?
The bug concerns 22.06.23 and 22.04.25 (and perhaps other also but not verified) - 64 bit
Can you repeat the problem? If so, what are the steps?
(Please be specific and use the names as seen in Shotcut, preferably English. Include a screenshot or screen recording if you can. Also, you can attach logs from either View > Application Log or right-click a job and choose View Log.)
Repeatable. When putting Text: Simple with empty text (containing only spaces) and colorful background, this colorful rectangle is visible on preview and on export frame. However when exporting video to mp4 it disappears (it looks like this filter is ignored).