Hi there,
I have a dockerised Confluence Server installation (6.14 or 6.15) on my instance. The issue is as follows:
Assuming I create a new page, with some standard emoticons in it [ for example: (/), (y), (!)]. Saving it displays everything fine. When I edit it however, the icons' sources that are already inside, shift to HTTP (after inspecting the url of the icons). So if I save the now edited page, all of the icons will not get rendered. In the case of inserting new icons, when editing, those will be displayed properly, but they will also have the same issue, after the next edit.
Any clue what might be wrong on my deployment?
Screenshots:
After creating the Page: 
After an edit to the page: 