Create a page with the title bug1 but don't save this page.
Create a another page with the title bug2 and don't save it either. The second page must be created with the same user, but this can be done within another browser tab or within a different browser.

Now add any attachment to the page bug2.
Save page bug1 and after it page bug2. You will see that page1 has the same attachment like bug2.

Both pages have the same temporary ajs-attachment-source-content-id which can be found in the html source code.

I think this must be fixed.

Is there a way to convert the ajs-attachment-source-content-id to the resulting pageid?

I want to add attachments to a post with my plugin but it's not sure if the page is still in edit mode or already saved.