Sorry, it's hard to see the mesh on the video but it looks maybe a bit tight? There should be a tiny amount of play in the mesh. Just wiggle it back and fourth.
Notice at around 2:30 he moves the gears and you can see the tiniest movement. Just a bit of clicking sound. You will need to move the...
It's hard to see how much engagement there is from the picture. But you want a little bit of play and it should not be "tight". The larger the gear pitch the more lash you can have.
For 48P gears, it's pretty tight and you should be able to get a piece of paper between the gears. For Mod 1...
A few options.
There is thread lock specifically for plastic. Although, I've never used it and don't know how reusable the plastic is afterwards.
This one is super glue based
https://a.co/d/4qrTEQZ
This one looks like it's more for mending.
https://a.co/d/2ix5Gnd
Another option is to see if...