P: When trying to add files to Collections I get this error: ?:0: attempt to compare two nil values

"Trying to use your workaround...but not seeing View > Sort as an option."

Go to Library grid view (e.g. type "g"). Then you'll see the View > Sort menu (see the screenshot):

*artthatsmiles Did it default to custom when it stopped working? Try changing the target collection to anything but "custom"?

Go to View Menu >> Grid View (G)

Then below the grid, change the Sort By Option to anything but Custom. 

@John_R_Ellis Hi John...Trying to use your workaround...but not seeing View > Sort as an option. Clicking on the collection I want to add from, going up to the menu, clicking VIEW and what next? There is no option to Sort in the View menu. What am I doing wrong?

I have the problem too, changing the order isn't working for me either. 

Helped for me to...Thank you.

Resorting the collection to one of the defaults from "custom" worked as a temp fix. It only started throwing the error after two hours of pulling photos for this particular assignment. 

Just upgraded to LR 10 and started getting this error. Here's my data:

Lightroom Classic version: 10.0 [ 202010011851-ef6045e0 ]
License: Creative Cloud
Language setting: en-US
Operating system: Mac OS 10
Version: 10.15.7 [19H2]
Application architecture: x64
Logical processor count: 8
Processor speed: 2.9 GHz
SqLite Version: 3.30.1
Built-in memory: 16,384.0 MB
Real memory available to Lightroom: 16,384.0 MB
Real memory used by Lightroom: 5,257.3 MB (32.0%)
Virtual memory used by Lightroom: 16,095.4 MB
Memory cache size: 1,103.6MB
Internal Camera Raw version: 13.0 [ 610 ]
Maximum thread count used by Camera Raw: 5
Camera Raw SIMD optimization: SSE2,AVX,AVX2
Camera Raw virtual memory: 546MB / 8191MB (6%)
Camera Raw real memory: 553MB / 16384MB (3%)
Displays: 1) 3360x2100

Graphics Processor Info: 
Metal: AMD Radeon Pro 460

Application folder: /Applications/Adobe Lightroom Classic
Library Path: /Volumes/OWC BACKUP/LightroomCatalogs/LightroomCatalog-OWCBU-v10.lrcat
Settings Folder: /Users/jamesparker/Library/Application Support/Adobe/Lightroom

Installed Plugins: 
1) AdobeStock
2) Aperture/iPhoto Importer Plug-in
3) Aurora HDR
4) DxO PhotoLab 4
5) DxO PhotoLab 4 Importer
6) Envira
7) Export to Photomatix Pro
😎 Facebook
9) Flickr
10) HDR Efex Pro 2
11) Helicon Focus Export
12) Imagely
13) jf Zenfolio
14) Luminar 3
15) Luminar 4
16) Luminar Flex
17) Nikon Tether Plugin
18) ON1 Photo RAW 2019
19) ON1 Resize 10
20) ON1 Resize 2019
21) Photolemur 3

Why conversations get merged: https://feedback.photoshop.com/conversations/lightroom-classic/lightroom-auto-import-to-folders-organized-by-date/5f5f44f14b561a3d422ab0ba?commentId=5f5f48984b561a3d422bdf45 

Thanks very much. That worked. Interesting that it hadn't occurred before