Electric Clocks

I have made 3 of these clocks and all of them run slow. For example, I set the clock at 8:30. By 11:00 it was already showing 5 min slow. This is after I modified some of the gears. The modifications I made were to the gear that mounts to the motor (gear 6). I modified the hole to fit the shaft so it cannot slip at all.

I modified gear 5-15 and 5-30 to have a 22 mm round flat friction surface and cut a groove in one of the surfaces to fit an O-ring hoping to create more friction. I am using a silk filament for the gears and I noticed they slide easily when rubbed together so there was little friction between the gears. Hence this modification. I have been checking the clock regularly and they do not seem to be slipping now,

All the gears turn freely and easily.

I replaced the RTC just in case that might be bad.

Even with these updates, it did not fix the issue.

Any advice on fixing this would be appreciated,