I just cloned the repo (on windows) and got the following warning:

warning: the following paths have collided (e.g. case-sensitive paths
on a case-insensitive filesystem) and only one from the same
colliding group is in the working tree:

'tests/data/pdb/1CRN/1CRN.pdb'
'tests/data/pdb/1crn/1CRN.pdb'

I'm pretty sure this is just duplicate data and one of the two can be removed. This should be confirmed, and if true one can be deleted (make sure that all tests point to the remaining data).