Thanks for contacting WPML forums support. I'll be glad to help you today.
1) Would you please try the following steps?
1- Go to Pages-> All Pages
2- Switch the language from the top admin bar to Croatian
3- Edit the Croatian shop page
4- Change its slug
5- Update the page
Kindly let me know if the above steps fixed the issue.
2) It's not related to the issue, but according to your Debug.info, the WP memory limit needs to be increased. PHP memory is fine, but WordPress uses 40Mb as default. The minimum requirements for WPML are 128 MB. (Kindly check this page https://wpml.org/home/minimum-requirements/)
You can increase it by adding the following code in your wp-config.php file right before the /* That's all, stop editing! Happy publishing. */ line: