Anytime Flexi becomes unstable like this it is normally best to clear preferences. We created the video at the below link to walk you thru clearing preferences in Flexi.
Just one warning, clearing preferences deletes the below information from Flexi and Production Manager and it will not be recoverable. Only do this as a last resort, especially if you have unfinished jobs in production manager that you need.
Jobs in Production Manager for all Devices.
Default job properties for the device drivers, it is best to take screen shots or write them down.
Device Drivers in Production Manager for all Devices (it keeps any profiles so you will not loose them).
Any customization to the Flexi Design Window.
Clear Preferences in SAi Flexi