Are you invoking Photo > Delete Rejected Photos (Ctrl + Backspace / Cmd + Delete) while in Develop? A number of people have reported that can freeze the most recent version of LR (CC 2015.8 / 6.8). If this is triggering your problems, please add your me-too vote and details of your issue to the bug report in the official Adobe feedback forum: Lightroom: Image stuck in Develop mode | Photoshop Family Customer Community
The workaround is to delete photos from Library mode, not Develop.
Which operating system do you use? Mac or Windows?
Have you tried to deactivate the GPU acceleration?
Edit->Preferences->Performance, uncheck Use Graphics Processor
Also take a look here: https://forums.adobe.com/message/7745890#7745890
Thanks. Use Pc have deactivated gpu
Sent from my iPhone
Are you invoking Photo > Delete Rejected Photos (Ctrl + Backspace / Cmd + Delete) while in Develop?