Title Merge submissions can inadvertently create self-referential VTs. To break them, you need to create a VT submission with "0" as the parent title ID. When it happens, the parent title fields of the title's VTs (if there are any) are also reset to 0.
Anonymous
Fixed in mod/ka_new.py, installed in SVN 680 on 2021-07-09. Closing the Bug report.