Dear Tim, thank you for your reply. I will be adding more info regarding the issue:
After the above-mentioned incident, this error was popping up when trying to attempt a quiz:
Another weird behavior we faced was having the PURGE ALL CACHE disappearing -- pic purge search attached
In addition, an error popped up on Completion progress: " An error occurred when attempting to save your tick mark ".
We tried changing our theme from Adaptable to Clean for a short while and then reverting back to adaptable. This made the purge button to appear again and we didn't face any similar weird behavior yet. My question here "Does changing the theme purge the caches, and if so, which cache?"