[Plugin: NextGEN Gallery] Losing preferences and translation on update

Hi

I really like the plugin and its features, but am facing an issue that may make me give it up: whenever I apply an upgrade, and I try to do so whenever updates come out for security reasons, I lose parameters such as thumbnails sizes, and the translation .po file gets deleted from the directory. I tried again just now and can see it’s gone.
Hence after I apply the upgrade, I get worried users because the French translation is all gone, and if they upload new images their thumbnails end up at a different size.
Am I the only one facing this ?
This is the latest WP on a Plesk server. Best regards.

https://www.ads-software.com/extend/plugins/nextgen-gallery/