Unable to edit browser shot

Hi
I added this new testimonial this morning. When I inserted the Browser Shot using the block from the block editor I was able to add the URL and the dimensions in the right column. However when I tried to add a caption I couldn’t get into the editor. I then tried to change the dimensions and in doing so inadvertently added “360300” as a caption, which I am now unable to remove. I am also unable to select the block at all, so can’t even delete it and start again. I generally use Firefox but have tried in Chrome with the same result. I think it has probably been caused by a recent update to WordPress?

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