This answer provides quite interesting plots of apogee and perigee for objects 41332 and 41333.
The primary (sine wave -like) oscillations are probably due to perturbations caused by potential generated by non-spherical Earth, as described in this answer (at least period of few months is in the same order of magnitude with apogee and perigee oscillations for Tiangong-1, as shown in a plot in the question body to the answer).
What does look interesting is the symmetry of these otherwise irregular secondary oscillations along vertical line connecting max/min values.
What is/are the reason(s) of these secondary oscillations?
Could it be a measurement noise/error or some weird processing artifacts, or is it indeed the actual behaviour of the orbiting bodies?