Blender crashes consistently when I use Extrude Pull two times as shown.

[raindropsfromsky]

System Information
Operating system: Windows-10-10.0.17763 64 Bits
Graphics card: Intel(R) UHD Graphics 620 Intel 4.5.0 - Build 25.20.100.6444

Blender Version
Broken: version: 2.81 (sub 3), branch: master, commit date: 2019-08-28 03:44, hash: rBf88022b96f3a

I cut the top of the default cube, with Make Line addon (by Manovii), and then pushed one part down using the Extrude pull addon.

Then I cut the lower part in two parts using the same method.
The result is shown below:

Then I pushed one part down using the Extrude pull addon.

The moment I release the LMB, Blender crashes.

[raindropsfromsky]

In this second experiment, I used the Knife tool to cut the top face of the default cube.
Then I pushed down one face with Extrude Pull tool.

Then I selected the lowered face, and used the Extrude Pull tool on it again.

As soon as I release the LMB, Blender crashes.

This also happens consistently, just like the first experiment.

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In a third experiment, I pushed down one face with Extrude Pull tool, and then selected the other half of the top face of the cube (i.e., the part of the cube that was intact), and used the Extrude Pull tool on it to push it down. Blender does not crash.

But if I use the Extrude Pull tool on the first face after this, Blender crashes.

In a fourth experiment, I cut the top face of the default cube with Knife tool, with a left-to-right stroke (along Y-axis). Then I selected the backside half of the cube, and used the Extrude Pull tool on it to push it down.

Blender crashes.

[raindropsfromsky]

I carried out the same experiments in Blender 2.80. It does not crash at all.