we have had this happen to us recently as well - thus here is what we found:
1. check your network and switch setup;
2. reduce file size, anythiany TW file beyond 3-4 GB i would start looking at very closely... check for anything superfluous in the project map (worksheets and sections);
3. check the library manager - some people load PLA's as libraries;
4. increase RAM on both server and workstations, the bigger the file the more RAM speeds things up significantly;
5. check your backup settings on the BIM Server - the default settings might contribute to your problem;
6. if you are running on Apple hardware ensure that WiFi is switched off on all devices;