There are at least two ways to fix this, one is to disable app nap entirely. You can add this to Info.plist.in:

+  <key>LSAppNapIsDisabled</key>
 +    <string>True</string>

The other would be to somehow cause the app to “wake up” whenever the tty client is used as well. I’m not sure how to do that, it may be trickier.

Aaron