Collapsing and uncollapsing Shader Graph Blend node creates visual artifacts

To reproduce:
1. Create a new project which supports Shader Graph
2. Create a PBR Shader for Shader Graph
3. Open the shader in Shader Graph
4. Create a Artistic/Blend/Blend node
5. Create a Input/Basic/Color node
6. Connect the output of Color node to Base of the Blend Node
7. Create another Input/Basic/Color node
8. Connect the output of second Color node to the Blend input of the Blend node
9. Collapse and uncollapse the Blend node

Expected result: The Blend Node looks like it looked before collapsing
Actual result: A visual artifact is visible. The Opacity input value seems to be "squished"

Reproduced on: 2019.3.0b1 SG 7.0.1 2019.3.0f2 SG 7.1.6
Does not reproduce on: 2018.1.9f2 SG 1.1.9, 2019.1.14f1 SG 5.7.2, 2019.2.16f1 SG 6.9

Cannot test: 2019.3.0a1, 2019.3.0a5, 2019.3.0a8 SG 6.5.2, 2019.3.0a11 SG 6.5.2 <- These versions have a different bug.