Lightroom Classic upgrade (9.2) of 30 March 2020 issue

[j_kiely_jr]

All – 
The latest version of LR Classic (9.2) on the Mac contains a bug of some type specifically around the act of selecting a number of images in grid mode and attempting to click and drag the group of selected images into a collection. When one does so the act of clicking and holding and dragging the entire group of images does not function smoothly anymore and the selection of 20, 30, 55, whatever, de-selects and becomes only the grid image on which you clicked and held. 

background: Given my current shelter-in-place life I decided to reorganize 20-odd years of personal digital files so I've been clicking and dragging much during the past couple of days. The only thing which changed today was before I had coffee I said "ok" when Creative Cloud pushed an upgrade my way. Ooops. The issue snuck up on me and for awhile I thought my mouse was dying or something with my double click or click and hold function. 
I crossed my fingers and jumped into Time Machine to fetch back the fully functional LR version (9.1) from yesterday. Thankfully that particular trick to downgrade worked in my case. I now have no problem doing what I need to do in sorting images as I'm running the older LR 9.1. Although, I might add, there is some type of memory or process leak going on as if one clicks and drags for a good bit of time the spinning beach ball shows up more and more and more as time goes on. Seems to go away after a restart. So there's that.

-j.

[Rob_Cullen]

And, are you dragging by first [click & hold] on the image portion of thumbnails, and NOT the grey borders?

"de-selects and becomes only the grid image on which you clicked and held." suggests to me that you are trying to drag from a grey border.

You might also find it useful to make one Collection the 'Target Collection' (Right-Click) , then pressing the keyboard [B] will add all selected photos to the Target Collection.