When I change frames per sec to 30 from 25 and have more than 1 video segment at more or less than normal speed (ie. 1.5x or 0.5x), one of the segments at the changed speed will be dropped from the final export.
“When I change frames per sec to 30 from 25 and have more than 1 video segment at more or less than normal speed (ie. 1.5x or 0.5x), one of the segments at the changed speed” does not sound “random” to me.
I reproduced this. Speed factor is relative to the project frame rate and obviously affects the duration of clips. Changing the frame rate at export is dangerous but can work on simple projects. I found a workaround: change the resolution at Export. This puts the export job into a different mode where the project is first rendered at its settings (click Master in Timeline and view Properties to see the project attributes) and then upsampled to the target resolution and frame rate. Not ideal, but then neither is your project settings.