Hi,
Thank you for the details!
I needet to debug this via the plugin editor, and I found the problem. When the index table was trying to apply the “the_title” filter on the reply titles, it bugged out for some reason. It may have been because the reply title is actually empty – however it should not cause any issues for WordPress. There might be a different hook also assigned to the “the_title” filter, and maybe that one was set off and causing a loop of some sort.
Anyways, I simply added a condition not to apply that filter when the title is empty, and it seems to have resolved the problem.
I will incorporate this in the upcoming release as well for sure.