I am suffering from the same issue since the outlook 52 on beta 5 and when updated to outlook 53 through the beta version it be came better but the issue still exists only when the message i am opening has multiple threads or it does include attachments. it doesn't matter you are using the new version or old version of outlook (layout) it does stuck only with these two cases attachments or multiple threads in the same massage. other than that everything is working. i have already uninstalled and installed back and nothing is working.