ComboBox.setItems() produces javascript errors when called in listener

When I set the items of a ComboBox within a listener (I tried both button click listener and combobox value change listener), the setting of the items will not succeed and I see 4 JavaScript-Error-Notifications:

(TypeError) Cannot read property 'confirm' of undefined
(TypeError) Cannot read property 'set' of undefined
(TypeError) Cannot read property 'updateSize' of undefined
(TypeError) Cannot read property 'reset' of undefined

Other methods like comboBox.setEnabled(false) do work within the same listeners.

I am using Vaadin 12.0.3 and the error is reproducable with a simple ComboBox<String>. I will post a codesample very soon that reproduces the issue.
Before I raise this as a bug in github, I would like to ask here if

  1. this is a bug at all or am I doing something wrong?
  2. if its a bug, is it known?
  3. Is there a workaround until fixed?

Oh, apparently this is a [known bug]
(https://github.com/vaadin/vaadin-combo-box-flow/issues/169).

The workaround is to initialize the ComboBox with an empty Collection.