So.... you leave A320 parked for ten days or more, supposed WTB test is no longer valid and on the first flight the computer (you don't know which) decides to test WTBs. The supposed test is usually done during landing yet the computer (you don't know which) decides to test it at random time during flight, locks the WTBs in process and leaves aeroplane without flaps or slats.
Plausible?
Neither do I think so.