to have forum members best help you, more details would be helpful such as the specific version number of PS you are using, OS type and OS version. Some versions of PS have issues with Smart Objects and bug fixes were implemented. Do you have the most recent updates for PS, your OS, etc.
I think that would be a good starting point. Just a suggestion.
Sorry if my question sounded to intrusive to answer. Was just trying to get the basic information to help forum members help you and be efficient with both of our times. No different than a medical Dr asking for medical history and/or specifics symptoms to better diagnose an ailment.
Without more specific information, I would suggest resetting PS Preferences file via this approach: Press and hold Alt+Control+Shift (Windows) or Option+Command+Shift (Mac OS) as you start Photoshop. You are prompted to delete the current settings. The new preferences files are created the next time you start Photoshop.
Not sure that will help yet its easy to try and get out of the way. Maybe other forums members will have additional thoughts.