Sandboxes with large packages in dependencies don't work anymore because jsdelivr has a 50Mb limit of package size. Previously, those sandboxes downloaded modules from unpkg. I think the issues appeared after this commit.
We are currently looking into ways of significantly increasing this limit at jsDelivr, but in the meantime, I'd recommend falling back to unpkg for requests that return 403 status.
We increased the limit to 100 MB (will consider increasing it further soon) so the sandbox should work now.
Can confirm, the sandbox in the issue is opening 馃挴, thanks @MartinKolarik!
looks like devextreme was somewhere between 50 and 100mb 馃槄