There are numerous subsidence maps for Quetta, maybe it is good to localize their displacement and compare it to your patterns.
Thr measurements from the reference show subsidence of to to 10 cm per year while yours largely range between +1 and -1 cm per year. I think the atmospheric disturbance superimposes these displacements in most image pairs. Did you select images from the dry seasons?
Otherwise you might get more stable results with persistent scatterer interferometry StaMPS - Detailled instructions