I took your example, and put it into a text file called q6.txt. I then imported this into my Moodle 3.6.3. It worked (see attachment). So, your problem doesn't seem to have anything to do with the version of Moodle. I think that your problems were in your upgrading of Moodle.
Consider going to Site Admin, Server, Environment, and posting a screenshot of what shows.
Ask the person who did the upgrade to explain how he upgraded, and then post this information.
Upgrading can be done from Moodle 2.9 to 3.6, but there are a lot of things that have to be done correctly, otherwise, problems can occur, as you discovered.
