Steps to reproduce:

1. Open attached project "ShaderGraphET.zip"
2. In Project window, open Assets/Bug.shadergraph
3. In ShaderGraph window, from the blackboard, drag the "Color01" property to the graph and connect it to the Lerp node's "A" input
4. In ShaderGraph window, from the blackboard, drag the "Color02" property to the graph and connect it to the Lerp node's "B" input

Expected result: The ShaderGraph window updates without issue
Actual result: The ShaderGraph window is broken

Reproducible with: 12.1.11 (2021.3.25f1), 14.0.7 (2022.2.19f1), 15.0.5 (2023.1.0b16), 16.0.1 (2023.2.0a15)
Not reproducible with: 10.10.1 (2020.3.48f1), 12.1.11 (2021.3.24f1)

Reproduced on: Ubuntu 20.04
Could not reproduce on: Mac OS 12.4

Notes:

1. Likely incorrect First Affected Version since reproducing the issue from 2020.3 to 2021.3 is really inconsistent
2. Switching to another Unity tab and back to ShaderGraph, or closing and reopening the graph fixes the issue