Cannot editing Iframe in Custom HTML Plugin

I have created an iframe where I added 3d tour from Matterport site. It has been working good but the model was removed so I wanted to update my iframe url. The issue is I cannot edit custom html. The moment I open it the custom HTML plugin closes on its own. Here is the video:!AlsKqWm66aENnmlvnUNGdBE-O772?e=QmJsQi

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