Nano banana pro auto change the characters’s face when I ask it to change the hairstyle

When I generate images with Nano Banana, I asked it to change hairstyle for one character, however Nano Banana automatically changes the character’s face or features, and I can’t get it to keep the same appearance across different images. See the attached images, how the face changes every step. And I had happened multiple times on different characters I used.

Has anyone else experienced this?
Is there a way to maintain consistent facial features with Nano Banana, or is this a known limitation of the model?

Any advice or workarounds would be really appreciated!