Question PolyBrush vanished from the project&package manager - Reinstalling it triggers 115 errors on Play

Hi there!

an artist in the team was using Polybrush 1.0.2 preview 4 (on Unity 2019.4.0f1)
As I upgraded other completely unrelated packages, Polybrush disappeared.

According to the logs, it was in the Package Manager, but never had its line in the Packages\Manifest.json

Someone else noticed it was missing, so it got installed back, now actually adding a line in Manifest.json.

The artist tho had some issues, as v1.0.2 (2019.4 Verified) was installed instead of 1.0.2 preview 4.

I assume the artist also used PB Verified for a week.

When I realised that his meshes weren't deserialised/serialised properly (the changes reverted after closing Unity), I suggested about rolling back to preview 4.

And...something's not right again.
When running the game from the splash screen (not from the scene to be tested), it now correctly shows the mesh (instead of a flat plane)

Yet

I get over a hundred of similar errors:



Is there any particular setting I have to tweak?
Is it normal that preview4 polybrush shapes can't be upgraded to the 2019.4 Verified version?

I'd really love if I could save the artist a lot of days of work because of this :S

Could you please help me solve this issue? (still no idea about how Polybrush automatically disappeared from the project while it's been in the package manager, but with no lines in the json file for it)