To uncrop thumbnails in galleries in WordPress:

1. Log into your WordPress.
2. Click the 'Settings' tab on the left of the screen.
3. Click the 'Media' option.
4. Unselect the check box 'Crop thumbnail to exact dimensions (normally thumbnails are proportional)'.
5. Click the 'Save Changes' button.

Note: Select the check boc 'Crop thumbnail to exact dimensions (normally thumbnails are proportional)' to enable gallery thumbnail image cropping.