P: Images not sharp unless I zoom in and out

i have found a few scenarios where (for me, 2nd monitor) the photo does not fully render unless you do something to it. the 2nd monitor will show a less than sharp photo, so i do a quick + then - (brightness up and down) and then it snaps into place. I have found other cases when doing autosync on multiple photos that only the first photo gets adjusted but the others don;t unless "touched" (for example, running a cursor over them in the filmstrip at the bottom of the screen). 

See also https://feedback.photoshop.com/photoshop_family/topics/lr-7-3-1-often-not-updating-rendering-in-full...

Simon,
I'll give you a code number: LRD-4197639

Ok. What is the version of LrClassic that you are running?

Do you see any render difference by toggling the details panel on or off? When Lr renders the image at less than full resolution (1:1), the rendering of the Details panel settings including sharpening would be an approximation. Can you share a copy of such photos plus the settings online? 

this is exactly what I tried to describe when I said I have to zoom in and out (1:1)  to get images sharp

This is a known bug and has been reported to Adobe, but it has not been dealt with yet. Indeed super annoying. What works is to zoom in to 1:1 and then zoom out again.

no, I am not using Smart Previews instead of Originals.

@129856 - no, I am not using Smart Previews instead of Originals.

Make the standard Previews big enough for your Monitor.

Did you have "Use Smart Previews instead of Originals for image editing" checked in the Lightroom preference dialog? Uncheck it if you always prefer Lightroom to load and edit the originals.