A company I use often, Wizz Air, had/has to regularly ground these planes. It’s always a safe bet to book seats at the front of the plane to be sure that your seat doesn’t magically disappear when you are at the gate (happened last Easter when they sold seats for a 180 seats plane but had to ground it and sent a smaller one last minute). The only silver lining here is that they caught the problems before any plane actually crashed because of them