Several times a day I find that the icons at the top of the messages disappear:

After a restart they're back to normal:

The buttons don't return when changing the theme, a restart is the only way I've found to resolve the problem. I only have one plugin installed: https://github.com/colinking/n1-unsubscribe
_Mac Version 0.4.56-816edde (0.4.56-816edde)_
Hey! Thanks for reporting this - I think I've found the relevant exception from our internal logs, I'll see if we can get this fixed in the next release. Just to be sure, next time this happens can you open the Developer Tools in the window (Developer -> Toggle Developer Tools) and copy any errors you see in the console at the bottom? (You may have to press Esc for it to appear).
It happened again this afternoon, here's the error from the Developer Tools console: http://pastebin.com/FXzZrh5H
Aw, it looks like that's happening because the n1-unsubscribe plugin is broken. Closing this issue for now鈥攜ou may need to open one with the developers for that plugin!
Most helpful comment
Aw, it looks like that's happening because the
n1-unsubscribeplugin is broken. Closing this issue for now鈥攜ou may need to open one with the developers for that plugin!