Suspended apps are unresponsive when brought to foreground

[Rüdiger Kupper]

Meizu MX4, OTA-10.1
In contrast to Ubuntu desktop, apps on Ubuntu Mobile get suspended (SIGSTOP?) when put to background, unless they have a life cycle exception. The app is to be resumed (SIGCONT?) when brought to foreground using the task switcher.
This used to work until OTA-10. OTA-10.1 introduced some change, the obvious visual improvement being the apps showing a screenshot of the last active state while being resumed.
But very frequently, after being resumed, the app updates its graphics but then is completely unresponsive. To make it work again, I need to kill it using the task switcher and relaunch it.
This happens very frequently after OTA-10.1, preferably when the app has been suspended for a longer time (several hours).