Couple of observed issues with the new Beta, one of which is quite annoying: some inbox emails are getting into a tight loop of synching and re-synching with the server, over and over and over again endlessly. The email shows up and then disappears and immediately shows up again. While that is happening the inbox item count is incrementing by 1 each time - even though there are no new emails actually coming in. Very strange. I have to go in under a different client, i.e. Android smartphone or IOS tablet, and read those specific emails from the server and then delete them.
The other issue I have encountered is replying to an email in a window only to have that window occasionally just go away, returning me to the originating email window. The reply window is still available but I have to re-establish it to finish my reply.
FWIW: I am a long time, daily user of emClient and this behavior is all brand new with the Beta client.