Clustered precincts in Santolan Elementary School, Pasig City reportedly experienced various types of PCOS machine-related issues. At least 3 clusters—383, 384, 380 had malfunctioning PCOS machines but were eventually fixed albeit delaying the voting procedure.

In at least 5 clustered precincts, the machines also rejected many ballots after several tries.  In clustered precinct 380, at least 10 ballots were rejected at around 7:20am; by 8:05 another 2 ballots were rejected.  In precinct 389, the PCOS machine malfunctioned for around 3 hours. It stopped accepting ballots after 42 votes were fed into it, while after 34 votes the PCOS machine in cluster precinct 394 also experienced similar error.

The machine in clustered precinct 400 also rejected at least 11 ballots at around 11 am but the ballots were eventually accepted by 12:54pm. In cluster precinct 395, ballots were alternately being rejected.  The rejected ballots are on the table of the BEI to be counted later. By 3:18 pm, the machine in clustered precinct 384 has ceased to accept ballots.  The machine rejected over 300 ballots, which were left on the BEI table.