LR doesn't see external hard drive after being left on overnight

Having an issue with external drive. Working on a Dell XPS 8700 I'll be working in LR and then will stop for the night. When I returnthe next day, the photos are still there but if I try to edit them that day I get an error. I ahve to restart the EHDs to get LR to see the original images so that I can edit. Once I disconnect and reconnect the EHDs I'm fine. Anyone else getting this?