i discovered that settings of PHP can have a huge impact on success or not.
1. set max_execution_time = 90 or 120s (not ideal because it proves that something is not fast enough performed, but it will help)
2. set max_file_size to 20M
those 2 settings can turn the failure to success... in my case it solved my issue with uploading (from computer directory) issues with woocommerce plugin...while directly from wordpress web directory, it was uploading and working well...
very weird as it is the same server and the same installation/plugin...
so something should be different in WP code regarding installation source.
