Some asset editors don't open, test scenarios are blank

Description of problem:
.gdst, .gre.drl and .gre.dslr asset editors don't open in DR4. "Loading..." popup appears but never goes away. Test scenarios opens but no editor is visible inside the tab.

In DR3, .gre.drl editor opened and test scenarios opened in default editor (displaying xml source). .gdst are broken since DR3.

Version-Release number of selected component (if applicable):
DR4

Steps to Reproduce:
1. sign in into kie-ide, go to Knowledge or select Project Authoring Perspective
2. in Project Explorer, go to uf-playground / mortgages / Resources or Test resources
3. try opening assets

Additional info:
attached screenshots