Cannot keep our FR5 status number when the reply also says failure

I changed the SDK under our little FR5 status display and found something sketchy in my own wrapper. It still takes the first number it can turn into a reading. The new reply has more than the reading in it, so a failed request can put a perfectly believable number on screen. I've got captured success and failure replies from this installed version. I'd rather make the display admit it has no current reading than preserve this apparently helpful fallback. What should I test besides those two captures before I trust the parser again?