Hello,
phpdocx extracts dpi information from the image if it's not set using the dpi option, and also its size and mime (getimagesize).
Please also note that file_exists PHP function may fail when using an URL:
https://stackoverflow.com/questions/10444059/file-exists-returns-false-even-if-file-exist-remote-url
https://www.php.net/manual/es/function.file-exists.php
If you send the image to contact[at]phpdocx.com the image, we'll test it using addImage with the same options you are using.
Regards.