The banner's transparent areas after website publishing are all black.
This issue is caused by a new method of website generation during the publication: the original image file can be converted (re-sized and cropped) in order to fit web page area, where it is to be placed.
It is a Presence Builder internal issue PPB-4315 and is expected to be fixed in future Presence Builder updates.
As a workaround replace converted image file (for example
./httpdocs/attachments/Header/published_image_4.png) with original one.