I have a strange issue with the GThumb+ plugin and rotated images.

When the plugin is enabled and I navigate to an album, the thumbnails show as below:



The arrows indicate the direction to the displayed image's top. Unless identified as "portrait", all images were taken as "landscape". Clicking into the images themselves, displays them in the correct orientation.

However, if I delete the first image from the album, the thumbnails show as below:



Turning off the GThumb+ plugin resolves the display issue.

Any ideas?

Piwigo 2.10.2
Operating system: Linux
PHP: 7.3.7 [2020-10-14 18:49:58]
MySQL: 5.5.57-MariaDB [2020-10-14 11:49:58]
Graphics Library: ImageMagick 6.9.4-8