need help for scrollbar on floating window

Hello

This patch is just a button that opens an help window of the m4l device I am making.
The behaviour is strange on my pc.
Is there someone to tell me if it's working for him/her ?

Here, the strange thing is :

- I click the "?!" button
- the help popup opens well
- but scrollbars are missing even if they are "on" in the patcher inspector
- try resize the window moving the top border (doesn't work with other borders...://
- the popup will crash
- click again on "?!"
- everything is working properly..
- ...until you close and open the device again

weird isn't it ?

thanx for your help !

Julien