Epic bugs found during rolled back state

Summary

Today we enabled the new epic experience on https://gitlab.com/groups/issue-reproduce. While the new experience was enabled, I create a number of epic records with metadata (labels, dates, health status, time tracking) and relationships (child epics, issues and descendant tasks, as well as related items (epics, issues). We then rolled back the new epic experience and reverted to the legacy experience. This activity was a test of the roll back process for preparation of the upcoming general release of the new epic experience to customers on SaaS.

We found the following bugs while in the rolled back state on epics created while the new experience was enabled and on epics which were created previously:

Bug description	Example link	Screenshot
Cannot comment on thread, received error.	issue-reproduce/egrieff-group-2&27 (comment 2153251167)
Cannot emoji react to some, not all threads.	Example 1: issue-reproduce/egrieff-group-2#27 (comment 2153327864) Example 2: issue-reproduce#66 (comment 2153329958) Example 3: issue-reproduce#65 (comment 2153248697)	Example 1: Example 2: Example 3: