I am making an app that is connected to a SharePoint list. I was able to get quite a bit completed and the editor in the browser went haywire. The data cards on forms were jumbled, background images failed to load properly, forms gave conflicting errors saying data source was not connected, but in the form properties the app was clearly connected. When you click to connect the data source, a message saying "Connecting Data Source" or something along those lines displays but never makes any progress.
The odd thing is that the app is working just fine in the published version. I even published when the browser editor was not working properly and the errors seen in the editor did not appear in the published version.
I cleared browser cache, cookies, history, etc. as other posts mentioned for problems encountered by other users. I have switched between, Chrome, Edge, and IE without any improvement. Other apps I have open just fine in the editor, I can't wrap my head around what is going on as it seems like something is corrupted in one particular app when you open in the browser editor.