Okay, I think I managed to fix this. It was not an issue with the plugin, but there was something wrong with the object cache. The update_option(..) wordpress function was not working correctly. Once I deleted some values, it cleared the cache and now works all right.
Not sure what the casue was though.
If there is some sort of agressive database or object cache active there, then it could explain it. If you clear that completely after updating any plugins/themes or making any changes on the site, then it should be all right in the future.