First, try to deactivate GPU acceleration and see if this helps.
Second, update the graphic card driver.
And, read here: https://helpx.adobe.com/lightroom/kb/lightroom-gpu-faq.html
If it does not help, post the exact type of your graphic card /GPU.
Graphics driver is up to day. It's an MSI 560 Ti 448 overclocked and water cooled to the max. Supports OpenGL 4.1.
Did deactivating GPU acceleration change something?
Look at the system information in the Help menu. Does LR list GPU acceleration as activated?
Deactivating seems to put things back to normal as with LR 5.7. It's a shame they roll out a feature that should significantly boost performance but instead completely hinders it. As a gamer I know it's a difficult process to get things just right, but being a gamer I am used to GPU optimization being priority #1 and therefore getting the most attention from software writers.