I expect the second "play" button to be pushed in and highlighted in the below screenshot. Reopening the GUI fixes the issue. The train scheduling GUI does not have this issue. This also occurs if the "5 s passed" wait condition is removed from the first stop.
[2.0.15] Space platform schedule doesn't update highlighted station button
Re: [2.0.15] Space platform schedule doesn't update highlighted station button
It does happen to trains as well if you open them from the remote view: