Summary

This issue is intermittent! You might have to try the reproduction steps a couple of times to reproduce. 

In both the Legacy Editor and New Editor when attempting to add comment to an attachment there are times that the comment text box doesn't render. Instead one of the below 2 things happens:

• A forever spinner is shown
• It loads blank

This seems to happen when either:

• Adding a comment for the first time
• Adding a comment to an existing attachment then navigating to another page and attempting to leave a comment on an attachment on the 2nd page.

If you inspect the browser console, you'll see the below console error:

com.atlassian.confluence.plugins.confluence-previews:annotation-plugin.js?assetVersion=1000.0.0-5bfebadd0573&externals=__local-default__&locale=en-US:150 Uncaught TypeError: this.errorCallback is not a function
    at e.<anonymous> (com.atlassian.confluence.plugins.confluence-previews:annotation-plugin.js?assetVersion=1000.0.0-5bfebadd0573&externals=__local-default__&locale=en-US:150:1128)
    at n (1.7.2.1-confluence-custom-m07.js:1:8777)
    at Object.fireWith (1.7.2.1-confluence-custom-m07.js:1:9798)
    at Object.fire [as reject] (1.7.2.1-confluence-custom-m07.js:1:9837)
    at Object.<anonymous> (com.atlassian.confluence.plugins.quickedit:quick-edit-general.js?assetVersion=1000.0.0-5bfebadd0573&externals=__local-default__&locale=en-US:13:6)
    at n (1.7.2.1-confluence-custom-m07.js:1:8777)
    at Object.fireWith (1.7.2.1-confluence-custom-m07.js:1:9798)
    at Object.fire (1.7.2.1-confluence-custom-m07.js:1:9837)
    at n (1.7.2.1-confluence-custom-m07.js:1:8777)
    at Object.fireWith (1.7.2.1-confluence-custom-m07.js:1:9798) 

Steps to Reproduce

Legacy Editor:

1. Create 2 pages with the legacy editor (Page A and Page B)
2. Upload an attachment to both Page A and Page B
3. Navigate to Page A
4. Click on the attachment and leave a comment
5. Close attachment preview
6. Navigate to Page B
7. Click on the attachment and attempt to leave a comment

New Editor:

1. Create page with New Editor
2. Add Attachment Macro to page.
3. Publish Page
4. Add attachment to Attachment Macro
5. Click the > next to the attachment
6. Click on view
7. Attempt to leave a comment

Expected Results

Should be able to add comments to attachments at all times

Actual Results

Can not add attachments when affected

Workaround

Currently there is not a workaround. However, we have seen that reattempting or using an incognito window will mitigate this.