the follow attached pic shows a warning/error appearing on "course details" front end.
originally the server was using php 7.0.16
I switched to 7.1.2 and cleared wp-rocket cache and this made no difference.
the site is a sub-site (multisite) so i "network deactivated" all multisite plugins as well as the individual plugins on the sub-site.
so basically there would be no plugins activated (except CoursePress Pro) and the warning/error would still show.
I painstakingly deactivated each plugin one at a time, then referred to the page with the error, even jumping around the site, refreshing the browser, and even using another browser, before moving onto another plugin to try to find a conflict without success.
I created a second dummy course with a unit and strangely the error left the first course details page of the first course and now only appears on the second.
the only difference i can determine here is that the first one i am enrolled in and the second showing the errors i am not enrolled in, so i am not even sure if and how this helps.
i have since activated back all plugins and granted support access if required.
currently using the newest version of WP as well as CoursePress Pro.
please feel free if required to create courses/units etc. to troubleshoot if required as it is a test site.
your very kind assistance in this would be greatly appreciated.