I just discovered Synchthing and tried setting up a basic system to test. I created a folder on my desktop machine with an empty text file in it and synced it to my phone - worked without a problem.
Then I opened that text document on my phone and added some text, saved, closed. This is where the problem occurred. Once the document synced back to my desktop, when I open it on that machine, the text document is just filled with 12kb of random characters. The only readable text in the entire thing is on the first line, where “[Content_Types.xml]” can be read among the rest of the random characters.
The interesting thing is that the document opens fine on my phone still, and I can read the text I added without issue.