Steps to reproduce:
1. Open the attached project "ShaderGraphTest.zip"
2. Open DiceGirl.mat using a text editor
3. Search for keyword "SGDissolve"
4. Navigate back to project
5. Right-click in the Project window and select Reimport All
6. Repeat step 2 and 3

Expected results: The number of occurrences of "SGDissolve" doesn't change
Actual results: One of the occurrences of the "SGDissolve" is duplicated resulting in an increased number of occurrences

Reproducible with: 9.0.0-preview.55 (2020.1.11f1), 10.1.0 (2020.2.0b9, 2021.1.0a2)
Couldn't test with: 7.5.1 (2019.4.13f1)

Notes:
- Not reproducible on Windows
- Seems to reproduce only a couple of times, after that it doesn't duplicate the property anymore
- Tested on Catalina 10.15.6