How to reproduce:
1) Load the attached project TextureArrayIssueProjectCreated19.3a10.rar.
2) Run the editor script Build/Build Course Texture Array.
3) Select the Textures/TextureArray.asset in Project window.
4) Set the wrap mode to Clamp.

Expected result: Wrap mode changes to clamp instantly/quickly.
Actual result: Preview changes to black immediately and that the editor locks up for a decent period of time.

Reproducible with: 2019.3.0a11, 2019.3.0a8
Not reproducible with: 2019.3.0a7, 2019.2.0f1, 2019.1.13f1, 2018.4.5f1
Couldn't test with: 2017.4.31f1

Additional note: On all versions, even the ones that are marked as "not reproducible" the Editor slows down a lot while the Inspector for the generated texture array is being resized