Forum Discussion
Modern document library view Group By not collapsing or showing second level
John Seto - i am also finding this to be true with lists with only a couple hundred items. Grouped/expand/collapse does not appear to be ready for the modern UI. It's pretty frustrating. I've had lots of clients go back to folders for now so their users don't abandon SharePoint altogether.
I know I'm replying to a 2 year old thread, but I recently had this issue and after much struggling I got it working.
The solution was to change the filtering (not the grouping). Although I was already filtering by indexed columns, I had 4 criteria, with a mix of and and or logic, and used begins with for some items. Simplifying the filtering resolved the issue. I think it is because when loading ungrouped data it can load incrementally, and tolerate more complicated filters, but when grouping it must load all data at once and gets overwhelmed.
I switched to using And logic exclusively, and avoided begins with, and it's working now.