Referencing this Bug (reported multiple times already and often closed:
https://developer.blender.org/T66254)

I am also experiencing this problem and have a file where it's showing up.

System Information
Operating system: Windows-7-6.1.7601-SP1 64 Bits
Graphics card: Quadro 5000/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 377.83

Blender Version
Broken: version: 2.83.3, branch: master, commit date: 2020-07-22 06:01, hash: rB353e5bd7493e

Notes on how to check this bug for yourself
I am currently running into this bug as well. It seems to be triggered when the strip in the layer above is moved.
I have created a quick scene to show the behaviour:

Steps to reproduce with the Scene:
Move the NLA Strip in the Layer called "Move This to the left" and watch the extrapolation mode on the strip below.

Here is the file in question: