When a small graph is drawn, for example several marks horizontally, a spinning spinner is visible at the edges.
.mw-graph has this: background-image: url (/w/extensions/Graph/includes/ajax-loader.gif?b3af8); and border: 1px solid transparent;
When there is something short on the graph and #tag:graph has "height": less than 47, then inside this border which is transparent is visible loader.gif and border flashes with gif animation
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one mark and spinner flashes inside the border around the mark
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"height":40 and the top and bottom of the spinner remains
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the spinner itself
This is not visible in Special: GraphSandbox since there is no .mw-graph but visible in pages and in Special: ExpandTemplates. Spinner was definitely not visible in 2018.