@roka Thank you again for logs provided. This line in a log tells that a Note with an Attachment was sent to a server (in one HTTP post action) and a server responded with OK (200):
08-24 04:19:03.008 V/HttpReadResult: ; statusCode:OK (200); url:'https://pl.smuglo.li/api/statuses/update.json'; authenticated; posted:'{"status":"Messed it up, again.","source":"AndStatus","media_part_name":"media","media_part_uri":"content:\/\/org.andstatus.app.data.FileProvider\/downloadfile\/at_19_0.jpg"}'; response:'{"activity_type":"post","attachments":[…'
The note was sent as a Multipart entity (see https://www.w3.org/Protocols/rfc1341/7_2_Multipart.html ). The entity is built in code here: org.andstatus.app.net.http.HttpConnectionApacheCommon#multiPartFormEntity
The same code is used for GnuSocial, Mastodon and Twitter. And it works there. So I would say that that Pleroma implementation should process the same content correctly also.
Could you get similar logs for a server side to know why the "media" part of the post was silently ignored or failed there?!