When we save an assemly as an stl it saves a bunch of stl files with the filenames of all of the assemblies they are in (starting from top level down) and then followed by a part name and -instance.STL

When there are a lot of nested assemblies the filenames are over 100 characters. 

Solidworks 2022 used to create these filenames and let them be long but Solidworks 2025 API truncates the name at 66 characters