Strange behaviour in percentage of completion of Gantt diagram

Question

Hello, PlantUMLers!

Playing with a Gantt diagram, I discovered that this (minimal working example) code

@startgantt
<style>
ganttDiagram {
    task {
        RoundCorner 1
    }
}
</style>

Project starts 2025-10-06
saturday are closed
sunday are closed
[Task] as [task] requires 20 days and is colored in lightblue 
[task] is 15% complete
@endgantt

generates this diagram:

As you can see, the % of completion (wrongly) appears at the beginning of each segment, with exception of the first and last one.

If I remove "RoundCorner 1" or set it to 0, it works well:

And even stranger... If I keep "RoundCorner 1" but remove "Project starts 2025-10-06", it also works well!

I think this is a bug but in case it is not, is there something I am doing wrong?

Thanks in advance!