  We report follow-up observations of the Crab nebula with the PolarLight X-ray
polarimeter, which revealed a possible variation in polarization associated
with a pulsar glitch in 2019. The new observations confirm that the
polarization has recovered roughly 100 days after the glitch. With the new
observations, we find that the polarization angle (PA) measured with PolarLight
from the total nebular emission has a difference of 18.0 +- 4.6 (deg) from that
measured 42 years ago with OSO-8, indicating a secular evolution of
polarization with either the Crab nebula or pulsar. The long-term variation in
PA could be a result of multiple glitches in the history, magnetic reconnection
or movement of synchrotron emitting structures in the nebula, or secular
evolution of the pulsar magnetic geometry.
