annoying vertical grey bar in pdf file

I managed to print a pdf from an HTML page with the htmlconvertTopdf xif extension using the user action GeneratePDF. All run smoothly except whenever appears one of the blue ALERT bars (rich widget) that trigger, in some way, the appearance of a vertical grey bar (pointed by a blue arrow) as shown in the attached file. How can I overcome this issue? Thanks!

it's the css. probably html/body or perhaps even .Page or .Content

try to reproduce it in chrome with the blue-alert and then check with dev-tools which css is causing it.