I encountered an intermittent bug in Adobe Illustrator where changing the Height (H) value of an object in the Properties panel → Transform section causes the object to unexpectedly flip vertically.

The issue appears to affect the Transform controls inside the Properties panel specifically.

The same operation performed using the standalone Transform panel (Window → Transform) works correctly.

What happened:

While working normally in Illustrator, I selected an object and changed its height using:

Properties → Transform → H

Instead of simply resizing the object vertically, Illustrator unexpectedly flipped the object vertically.

For example, an object containing text or directional artwork would become upside down after changing its height.

Important observations

I initially suspected that this might be caused by the object itself, such as a negative scale, an inherited transformation, a rotated object, or a corrupted bounding box.

However, I was able to determine that this was not the case.

The issue also occurred with a completely new rectangle in a completely new Illustrator document.

I then performed the same height adjustment using:

Window → Transform

The object resized normally and did not flip.

This indicates that the issue appears to be isolated to the Transform controls within the Properties panel.

The issue is intermittent

Unfortunately, I cannot currently reproduce the problem reliably.

It occurred sporadically during normal use. After I noticed the behavior, I tested it several times, including with a new document and a new rectangle, but the issue eventually stopped occurring.

I completely quit Illustrator and restarted it. After restarting, the Properties panel behaved normally again.

I did not make any changes to the document or artwork before restarting Illustrator.

Current behavior

After restarting Illustrator, I have not been able to reproduce the problem.

This makes me suspect that the issue may involve a temporary internal state of the Properties panel or Illustrator's transformation system rather than a problem with the document or artwork.

What I was able to establish
The problem occurred in a new Illustrator document.
The problem occurred with a newly created rectangle.
The problem occurred when changing Height (H) through the Properties panel.
The object unexpectedly flipped vertically instead of simply resizing.
The standalone Transform panel worked correctly.
The problem disappeared after completely restarting Illustrator.
The problem is intermittent and currently cannot be reproduced reliably.
Expected behavior

Changing the Height value in:

Properties → Transform → H

should only change the object's vertical dimensions while maintaining its original orientation.

Workaround

When the problem occurred, using:

Window → Transform

instead of the Properties panel worked correctly.

Completely restarting Illustrator also resolved the issue.

Illustrator version

I am using the latest/current version of Adobe Illustrator available at the time of this report on macOS.

Possible cause:

I suspect that the Properties panel may occasionally enter an incorrect internal transformation state, potentially causing a negative Y scale or an unintended vertical reflection when applying a height change.

The fact that:

• the standalone Transform panel works correctly,
• the problem also occurs with newly created objects and documents, and
• restarting Illustrator resolves the problem

seems to indicate that this is an intermittent Illustrator UI/transformation bug rather than an issue with the artwork itself.

Please investigate whether the Transform controls in the Properties panel can occasionally apply an unintended vertical reflection when changing an object's height.