I am having the same problem: In a particular campaign, there are two consecutive paragraphs that are both using size 14 Arial. The two paragraphs look the same in the editor, and the same on the Desktop preview. However, in the mobile preview, they look different: the font in the second paragraph looks lmuch bigger. This is in the Preview before the campaign is even sent. This is the first time I have noticed it, so I can't say it is happening with all campaigns.
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