  The prompt emission, X-ray plateau, and X-ray flares of Gamma-ray bursts
(GRB) are thought to be from internal dissipation, and the magnetar as the
central engine with propeller fallback accretion is proposed to interpret the
observed phenomena of GRBs. In this paper, by systematically searching for
X-ray emission observed by Swift/Xry Telescope, we find that seven robust GRBs
include both X-ray flares and plateau emissions with measured redshift. More
interestingly, the X-ray flares/bumps for those seven GRBs are simultaneously
observed in the gamma-ray band. By adopting the propeller fallback accretion
model to fit the observed data, it is found that the free parameters of two
GRBs (140512A and 180329B) can be constrained very well, while in the other
five cases, more or less, they are not all sufficiently constrained. On the
other hand, this requires that the conversion efficiency of the propeller is to
be two or three times higher than that of the spindown dipole radiation of the
magnetar. If this is the case, it is contradictory to the expectation from the
propeller model: namely, a dirtier ejecta should be less efficient in producing
gamma-ray emissions. Our results hint that at least the magnetar central engine
with propeller fallback accretion model cannot interpret very well both the GRB
X-ray flares simultaneously observed in the gamma-ray band and the X-ray flares
of GRBs with a high Lorentz factor.
