Page is not responding after add a report to a Book

Summary:

Hi,

I tried to add a report to a Book, but after I clicked the add button, my page was not responding.

I tried in new private/incognito windows and cleared the cache, but it's still the same.

Previously, I tried to open the Book and open it as Excel, but the loading takes forever.

So, I decided to create a new one and then this happened.

Is this a bug or what?

Thanks in advance.

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