Upon further investigation, I believe that this issue was confined to displaying the columns for "Entry page" or "Exit page" on the "Edit chains" page, when one of the TaskChain activities specifies a particular activity by name as either the "Next activity" or "Previous activity".
The URL of the page was something like ...
- /mod/taskchain/edit/chains.php?tab=info&chainid=999&columnlisttype=chains&sesskey=12345aBcDe
The issue is fixed in the latest release of the TaskChain which I have just made available via github.com and moodle.org.
Please upgrade the TaskChain module on your Moodle site at the next convenient opportunity.
Thanks for bringing this issue to my attentionregards
Gordon