I had a similar experience measuring gravity in high school. Our method was using a ticker timer.

One of these. https://www.physicsforums.com/threads/the-history-of-ticker-...

The inevitable happened, after the years of classroom abuse the timer provided enough friction that the falling object swung on the paper like a pendulum and slowly made its way to the ground over the course of about 5 seconds.

We analysed the meaningless dots on the paper and wrote up a calculation of gravity of 9.6m/s^2 attributing the 0.2ish to 'possible friction or accuracy of the timer'

This taught me more about science than I care to think about.