idlk files keep appearing and won't delete

We recently upgraded to the latest version of InDesign and ever since, we get several .idlk files that won't delete, even after the original file is properly closed. It happens to multiple users, even the one who originally created the file. We can't manually delete the file unless we exit InDesign and go directly to the server where we have the file saved. It's time consuming having to shut down InDesign multiple times a day. Does anyone know why this keeps happening and what we might do to stop it? Thanks