Army Air Corps pilots usually fall for that old trick of squawking 8/9 digits.
Andyb79 we get you to Squawk 0000 to indicate transponder failure following a recycle instruction. If a corrupt code still exists, the you would normally be instructed to switch off the transponder. However, where approved by local procedures and provided the Mode C has been verified, the corrupt code may be retained to assist identification and tracking. Associated ATS units are to be informed of the retention of corrupt data. With a corrupt Mode C if independent switching of Mode C is not possible you would be instructed to select Mode 3/A code 0000 to indicate a transponder malfunction.
Hope that helps from the military side.