Looking at the second screenshot, it seems like the question and answer fields are generated by the Advanced Custom Fields (ACF) Plugin with Repeater add-on. The symptom that only the item number is tracked, but not the item contents, reinforces this assumption. The ACF Plugin can either be installed as a plugin, but I think the necessary code can also be included directly in a theme.
As ACF saves the data in post meta, you should try the feature plugin WP-Post-Meta-Revisions. This plugin was made to bring post meta changes into revisions.
About the problem of disappearing content in you repeater fields: This could be because of limitations in your server config. If you are having many fields, you are probably hitting the input vars limit. Most configurations set max_input_vars to someting like 1000. Increasing this with php_value max_input_vars 5000 in your .htaccess file should help then. There is a thread about this in the ACF Support Forum