Would suggest you to make a copy of the catalog on the local SSD drive and check if it works well there.
Could you please confirm which version of Lightroom are you using?
Which operating system and the configuration including memory and RAM?
Ok, I'll try that.
Lightroom version: CC 2015.3 [ 1052427 ]
License: Creative Cloud
Operating system: Windows 10
Application architecture: x64
System architecture: x64
Logical processor count: 12
Processor speed: 3.4 GHz
Built-in memory: 32675.5 MB
Real memory available to Lightroom: 32675.5 MB
Real memory used by Lightroom: 1126.4 MB (3.4%)
Virtual memory used by Lightroom: 1075.5 MB
Memory cache size: 1239.8 MB
Maximum thread count used by Camera Raw: 12
Camera Raw SIMD optimization: SSE2,AVX,AVX2
System DPI setting: 144 DPI (high DPI mode)
Desktop composition enabled: Yes
Displays: 1) 3840x2160, 2) 3840x2160
Input types: Multitouch: No, Integrated touch: No, Integrated pen: No, External touch: No, External pen: No, Keyboard: No
Graphics Processor Info:
Check OpenGL support: Passed
Vendor: NVIDIA Corporation
Version: 3.3.0 NVIDIA 354.35
Renderer: Quadro K4200/PCIe/SSE2
LanguageVersion: 3.30 NVIDIA via Cg compiler
Application folder: C:\Program Files\Adobe\Adobe Lightroom
Library Path: J:\LR 5 data-4.lrcat
Settings Folder: C:\Users\Studio One\AppData\Roaming\Adobe\Lightroom
I Have a QUADRO K4000 card ...is your GPU being used by Lightroom ...You can get a report under the Performance menu.?
Lightroom does not pop a screen in my case to say my GPU has been disabled....
Is your GPU an officially adobe supported GPU?