Our angular project that includes this component quit building today. Upon investigating, it seems that mobx was updated and it is no longer compatible with the tree. Here is an example of a forked version of your plunkr:
https://plnkr.co/edit/y6KWNYXbJtwDfWUsWMI3?p=preview
All I did was update the mobx version from ^3 to ^4.
The workaround for now was to install a version 3 of mbox so it doesn't implode.
Yes, I'm getting the same issue here. But updating mobx did not make any difference. Still getting warnings
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errors like this:

Temporary solution:
npm install --save-dev [email protected]
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True, angular-tree-component had >=3. I'm changing to ^3 and publishing in the coming hour
Published - can you try with version 7.0.2-beta1?
I just tested with 7.0.2-beta1 and am no longer getting the mobx error.
Published in 7.0.2
Most helpful comment
Temporary solution:
npm install --save-dev [email protected]