Error popup on mouseover event with the custom command buttons bar

If the custom command buttons bar is not anchored (so a floating bar), I got an error message when the mouse is over a button.(see the attached screen capture)

This happens after upgrading winscp (winscp 5.8 beta Build 6030 on a Windows 7)

Note: However the related custom command is run after clicking on the button.

Thanks for your report.

This bug has been added to the tracker:
https://winscp.net/tracker/1385

I'm sending you an email with a development version of WinSCP to the address you have used to register on this forum.

Indeed with your latest version (5.8.1 Dev Build 6096), failure messages disappeared on mouseover events with any floating toolbar.

Attached my rnd file