project_task_dependency - selector field does not show for users

[leoniscsem]

Module

Project Task Dependency

Describe the bug

Parent task selection field does not show up for non-administrative users.

To Reproduce

Affected versions: project_task_dependency 15.0.1.0.0

Steps to reproduce the behavior:

1. install module
2. set permission in user configuration to Use Task Dependencies
3. open/edit a task in a project and look for the input field
4. It does not matter wether the task was created by another user oder the user himself.

Expected behavior
When a user with the given permissions edits a task, the input field for selecting a parent task should show up and give the option to select other tasks.

Additional context
Ubuntu 22.04
Python 3.10
Odoo 15 installed from source with virtualenv

[leoniscsem]

I did a fresh install (same codebase, new database) and everything worked fine. Both admin users and regular users could see the input field Parent task. Out of the blue it stopped working and the field disappeared for all users. After uninstalling the module, all the settings were still present: In settings → project I still could generally configure whether there should be task dependencies on projects. On the individual project settings I could also configure task dependencies to be available.
After a restart of the Odoo application, the entries were still there.
I do not know which db entries or tables to remove, so I gave it a shot to reinstall the module. The administrative user can edit parent tasks now, while other users still do not see the field showing up. It does not seem to make a difference if the user has the permission to use task dependencies defined in the invidiual user settings. Is there any way to purge the module completely and start fresh?

I have installed a few other 3rd party project modules, yet I cannot determine which ones might collide with project_task_dependency. One module is Project Task Milestone that possibly interferes, but debugging did not give me any hint. Where to check, what to look for? Milestones and task dependencies are incredibly important for our organisation, so I am trying to get a better understanding for what might be a possible solution.

Edit: I just realised even as admin user I can only see the input field in debug mode, but not when in regular administrator mode.