Problem:
active-post-lock - not able to edit entries
Solution:
You can always check for the possible conflict between the third-party plugins and theme to ensure there in no conflict between any plugin or theme you are using.
Please try to resolve your issue by deactivating all third-party plugins as well as the default theme to check for any possible conflicts with any of the plugins or themes? Do you see any difference?
I created 2 custom fields of type "Select" in this post type.
Options of these 2 select fields must be the titles (text) and postid (value) of all available projects.
BUT the select fields each show only 5 options, while there are 8 published projects.
Solution:
Please try to add Pagination limitation parameter in $args, for example:
