I have used the app on a number of iPhones and have updated versions of operating system and app. I store mp3 in the dropbox and use the app to listen, audio books and music. I hit pause in the app.
Later when I do something like switch the phone on or plug something in or am doing something where the Dopbox app is not even on the screen the file starts playing. It can be annoying because maybe somebody was sleeping in the room, or maybe I don't notice it and it runs the battery and I lose my place in the book. It was like this on my last iPhone 6 last year and the same thing is happening on new iPhone X and is now consistent enough as to cause me to drop you a line. Maybe we could promote this to 'known issues' as it is clear that something else can trigger that 'release pause' function.
This is happening to me too just this past week. Even when the app has been closed and i’m in airplane mode, Dropbox opens itself and randomly starts playing the last audio file I had open- four or five times a day, quite the fright at 6:15am this morning...
I deleted and reinstalled and have not had the same problem. I notice it was when something else was attached to the phone like a car stereo or headphones though the headphone jack with control potential, e.g. my iphone headphones have a button on them, maybe it can act as a play button and sometimes it is plugging that jack into the phone that triggers it playing.