Malfunctioning PCOS machines make up the bulk of election day problems in various Luzon provinces, based on field reports received by Kontra Daya.

The reports on PCOS machine glitches are varied and widespread.

Common problems include PCOS machines failing to initialize, short circuiting, and rejecting ballots. In many of these cases, the technicians are either missing or unable to fix the problems. Some impatient voters have given up and gone home after hours of waiting for PCOS machine repairs.

Many BEIs have stopped receiving ballots due to PCOS machine breakdowns. Others respond to the rejected ballots by trimming the edges of the ballots such as in Baguio, in effect tampering them.

In Baguio City, four precincts in Rizal Elementary School have been declared with failure of elections by COMELEC after its ballots were switched with those of Brgy. Gabi Elementary School in Compostela Valley. Special elections, yet to be announced, will be held for the 638 voters affected by the mix-up.

Other problems reported are the following: military presence, illegal campaigning, vote-buying, PCOS machines reading votes with improper shading, LGU officials interfering in polling areas, and disorganized poll watchers and BEIs.

The bulk of the reports were received from Antipolo, Aurora, Baguio, Bulacan, Dasmarinas, Tanauan, Bacoor, Lipa, Pampanga, Puerto Princesa, Quezon Province, San Pablo, Sta. Rosa, and Sorsogon.