Jay
Lets unpack this.
The high SWR is a failure of the TG-XL/PG-XL and Flex to communicate the antenna in use...so you do not get the correct tune solution. Be sure to use the latest Flex and TG/PG firmware, and I have found starting the TG and PG, after the Flex is booted up, ensures the necessary subscription requests and status messages set up the communications between all three.
Next, Flex lockup when running, or not, the Flex AppImage. When you run the AppImage, you will see the new modes, FDVU and FDVL. If something happens to ki$$ the AppImage PID, Flex becomes upset because it wants to continue with the new modes.....so it takes itself off line. The solution is to first, change modes so neither of the FDV modes are in use by Flex. Then, if you want to stop the FDV AppImage, use the control C combination to stop the AppImage...This will gracefully allow Flex and the AppImage to stop the waveform.
Alan. WA9WUD