P: Slider Lag

In Photoshop 2020.1, when dragging sliders (e.g. in Levels, but in other slider-containing dialogs as well) there is a significant lag before the screen redraws (Preview enabled). The screen doesn't start to redraw until I stop dragging the slider; there is about a 0.5 second or more delay before I can see the effect of the change. Photoshop 2019 does not do this, on the same computer; the slider change effect is shown continuously and smoothly in the preview as the slider moves. This is happening even with very small images (1000 x 600).

This makes fine adjustments very difficult to do, since I can't see the effect as it happens.

System information:

Adobe Photoshop Version: 21.1.0 20200212.r.106 2020/02/12: 4dd027efb58  x64
Operating System: Windows 10 64-bit
Version: 10 or greater 10.0.18362.329
System architecture: Intel CPU Family:6, Model:14, Stepping:13 with MMX, SSE Integer, SSE FP, SSE2, SSE3, SSE4.1, SSE4.2, AVX, AVX2
Physical processor count: 8
Processor speed: 3000 MHz
Built-in memory: 16318 MB
Free memory: 11196 MB
Memory available to Photoshop: 14929 MB
Memory used by Photoshop: 75 %

I have tried many suggested "performance enhancing" preference settings, but they don't help. Current settings:



I have two scratch disks set up, with the main one on an SSD.

My computer is certainly fast enough that there should be no lag, and there is no lag in PS 2019. Am I missing some setting or tweak that would eliminate the lag? Or is this a known problem in PS 2020.1?

David