Hello folks,
We kind of made it a tradition in Roundcube to add some nasty bugs with every second release we publish :-)
This time a pull request accidentally was merged into the release branch instead of git-master where we usually do the testing. The effect of this bug is the compose screen randomly reloading and likely loosing the contents you're writing. There's a patch you can download [1] and apply to any 0.8.3 installation. And a new release will follow later this week.
We'd like to apologize for this inconvenience!
Best,
Thomas