PAP lost their confidence after the losing Aljunied GRC. PAP do not want to be seen giving up on the GRC so they had been placing their lower tier grassroots leaders in that areas to make their presence felt with little effort. These are the ones that are lower quality than Sitoh Yih Pin.
The PAP candidate, Ong Ye Kung, is now redeployed to Sembawang GRC to prepare him for the next election. This is the problem with GRC system, even if someone who had been proven to be "rejected" by the citizen, the politicians can still forced their way through by putting the candidate in another area.
Instead proving that they are determined to serve the people, they become quitters and just jump ship to another GRC that is easier to get into politics.