First try to reset the Photoshop-CC2018 preferences.-
| To restore preferences quickly using a keyboard shortcut: 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. |
Second, check you are not developing in Lr using Smart Previews. (SPs cannot be opened in Ps by [Edit-In] )
Third, reset the Lightroom Preferences
How to set Lightroom Classic CC preferences
Is there anything else unusual about your workflow?