it could be a loss of hydraulic pressure or a flat battery if this happens after a while of flying. Not sure if thiese planes use either of these to power the controls, even if it's not accurate, they could be set up like that in the air files/cfg. Is there a generator switch on either of the planes panels, if so turn it on?
does this happen to just these two, or others? Unlikely to be hardware if it's just these two.
Other than that, dunno, don't have them installed to try.
Jamie