Modern list stuck with classic edit form

I had a standard custom list in a team site - basically the title and a quantity field - using it for a quick chart web part.

Playing around, I went to the list settings and opened up the content type management, and added the 'Task' content type to the list. So now it's got 2 content types - Item and Task.

The views still look modern, but when I click to edit, I get a classic edit page. OK, figured having the 2 content types threw me back into classic since Task list is a classic style.

Reversed what I did - removed the Task content type, removed all the fields from that content type, and set the content management flag back to No. Checked everything I could find and it says it's a new experience list.

I've even check it through SharePoint Designer.

But it's not! I can't get it back to edit in the new experience.. In list settings I've looked at form settings (use default), in advanced settings I tried forcing it to 'new experience'. but I'm still getting a classic edit form on a modern list. 

Has anyone run into this weirdness before?