When GlideElementRelatedTags creates the RelatedTagsOptimizer and adds it to the parent GlideRecord, it immediately tries to use the new optimizer to retrieve data for the current iteration. The optimizer will not actually have any data until the next iteration, after the GlideRecord asks the optimizer to populate itself.
Steps to Reproduce
No steps to reproduce available.
There is no known workaround for this issue. If you are able to upgrade, review the Fixed In field below to determine the versions that have a permanent fix to this issue.
Related Problem: PRB629310