Outlook on the web reaches an unstable state when Office.context.mailbox.item.saveAsync is called when attachments are uploading

Question

1. Open Script Lab with the following code sample:

    $("#run").click(run);
    function run() {
        Office.context.mailbox.item.saveAsync(result=>console.log(result));
    }

2. Attach multiple attachments (attach at least five for a getting enough time to perform the next step).
3. Click the "Run" button in Script Lab.

The behaviour after the above step varies greatly from each attempt. The outcome can be any of the following (or a combination of them):

1. An error message will appear: The following attachments coudn't be added: <Attachment name>
2. On attempting to remove an attachment, an error message will appear: The following attachments couldn't be deleted: <Attachment name>
3. An attachment which is visible in the compose pane may not show up on the corresponding Graph API (/me/messages/{mailId}/attachments)

This strange behaviour is observed only on Outlook on the Web. Desktop clients behave as expected.