Back in December during the Malacca ride, my chain broke. Since the pin was missing, I got to a bike shop and had it fixed for RM4.
Ever since then my chain would come off when going upslope. As time went by, it became worse and eventually, I was reduced to riding my bike as a single speed.
Decided to get to the root of the problem today and discovered a chain link that had been spread apart. It is proably why the chain kept skipping and auto-shifting. Hope the problem is solved for now.