In some cases, the current attribute used to identify images, which need to expand when clicked, in the Help Center theme fails. A generalization of the query can make this functionality more stable.
For me, it was solved by Confluence update to the later version. The problem had been found on 6.12 and and now on 7.4 it’s gone.
Thanks for letting us know. We’ll keep this open to see if more users are possibly affected.