The New York City Board of Elections estimates that 80 out of 1,300 poll sites did not open on time for last month's primary.
Voters reported multiple problems during the Sept. 14 primary, when New York state rolled out new automated voting machines for the first time.
Board of Elections officials described their preliminary analysis of the problems on Monday.
Executive director George Gonzalez told a City Council hearing that the board had received 2,470 calls reporting problems to its phone banks on primary day.
Some poll sites opened late because the new machines took longer to set up. A few machines also reportedly broke down after voting began.
Gonzalez said the Board is figuring out how to make the November election work better.