Collection trouble after upgrade

Looks like a bug to me, perhaps with syncing collections with the LR cloud.  I suggest you post a bug report in the official Adobe feedback forum, where Adobe wants all bug reports: 

https://feedback.photoshop.com/photoshop_family/categories/photoshop_family_photoshop_lightroom .

Be sure to include the first ten lines of the menu command Help > System Info and the screenshot (you can directly insert the screenshot in that forum).  Provide all the details, rather than linking back to this thread -- experience shows that Adobe developers tend not follow the links.

[Use the reply button under the first post to ensure replies sort properly.]

Two initial troubleshooting steps:

1. Please copy here the first ten lines from the menu command Help > System Info.

2. Make a full-resolution screenshot of your entire LR window and attach it here. To attach a photo here: After posting the reply, click More > Edit Reply at the bottom of the reply. Then click the little paperclip icon in the lower-left corner of the reply box. Then click Apply Edits. (If you insert a photo rather than attach it, the stupid forum software will reduce its resolution and hide important details.)