Meteor Tracker.autorun doesn't update after changes in code structure

Question

We are just about moving away from meteor in the backend (as the builds take longer and longer and other reasons) and have just moved a lot of core code (shared types, etc.) to a "shared" folder within our repository in order to use the type definitions in the new backend as well.

After three weeks of developing, I now wanted to test if the legacy meteor backend still worked. well, it does, however the legacy client which is also built by meteor suddenly wont do anything reactive.

The following code just prints "Tacker Update 0" and multiple times "Interval"

let i = 0;
dep = new Tracker.Dependency()
Tracker.autorun(() => {
   dep.depend()
   console.log(`Tracker Update ${i++}`)
})

Meteor.setInterval(() => {
   dep.changed();
   console.log("Interval")
}, 1000);

When doing a

Meteor.setInterval(() => Tracker.flush(), 100)

the tracker seems to "work", however that shouldn't be necessary, there is some obviously problem in the code that makes the Tracker non-functional, but I have no clue how to find it as git-bisect won't work here (made the new backend functional first while ignoring the old one with import paths etc).

Any ideas where I could look?