Occasionally, only one line of text is shown in link previews, with the fade-out at the end of this line, instead of the usual 7 lines of text. This seems to occur mostly in articles with only two sentences in the lead, or an otherwise short lead, but most short-lead articles show correctly (it shows the full text of the lead, with no fade-out).
Example: page – link preview
This is a response to CKoerner (WMF)'s reply on this topic.
P.S. It would be nice to be able to change the number of lines shown in a preview, or otherwise have more customisability with the gadget.