I struggled with this for a while but wanted to share what I did to fix it.
I was receiving the “async-upload.php” error in my browser console mentioned in the beginning of this thread. After trying almost every fix in the thread, I remembered seeing something about apache. This led me to check my apache logs which pointed me in the right direction:
[Wed Feb 12 13:29:34.636401 2020] [ssl:error] [pid 12207:tid 140213057730304] [client xxx.xx.xxx.xx:0] AH02018: request body exceeds maximum size (131072) for SSL buffer, referer: https://xxxxx.com/wp-admin/upload.php
[Wed Feb 12 13:29:34.654627 2020] [ssl:error] [pid 12207:tid 140213057730304] [client xxx.xx.xxx.xx:0] AH02257: could not buffer message body to allow SSL renegotiation to proceed, referer: https://xxxxxx.com/wp-admin/upload.php
After removing the SSL certificate and reinstalling it (auto SSL) I am not able to upload images successfully.
Hope this helps!
