I was able to send files to device (windows 10 too), as well as attach multimedia files in post to FB.
Strange, are you on the latest release? Maybe you can attach some logs for me to check on it.
*if you just granted storage permissions, you need to restart the app else storage permission won't work
Thank you for your answer. I managed to clean the cache and dalvik in recovery. From now on I can attach media files in FB applications.
As for BT - I've tried sending files to another android phone and linux pc and it's ok. The problem is only in communication with Windows. So I bet on the problem of Windows, not this ROM.