Hi Max,
this is a known issue with the Corbu theme.
See note 1832373 - PA30 scrollbar overlap.
A workaround would be to change the theme of the WEBGUI service from sap_corbu (current theme that you use) to the sap_tradeshow theme.
See the note.
1656975 - How to set the theme for SAPGUI for HTML?
However rather than setting the theme in the URL as outlined in the note.
Set the parameter
~theme sap_tradeshow
in the 'GUI Configuration' section of the WEBGUI service in the transaction SICF.
Regards,
Oisin