For certain abstract groups, the subgroup diagram sometimes appears to have question marks ("?") in the diagram instead of the group names.
E.g. For the group 128.3:
https://www.lmfdb.org/Groups/Abstract/128.3
Interestingly, this only seems to be an issue on the production server. Beta appears to render the subgroup diagram just fine: https://beta.lmfdb.org/Groups/Abstract/128.3