In English Wikipedia, the hatnote en:Template:Outline is shown in the Hovercard instead of the first sentence of the lead section. I modified it to wrap it inside the en:Template:Hatnote as other hatnotes like en:Template:For (which is not shown in the hovercards), but is still shown in the hovercards. Is something related to the cache and will be corrected after some time, or something else must be done? Thanks!
Topic on Talk:Page Previews/Flow
Yup, it's related to the cache. If I edit one of the articles that uses it (w:Special:WhatLinksHere/Template:Outline) that will result in a hovercard without the template. The rest should eventually update via the normal cache mechanism (but I'll ask a dev, to confirm). Thanks for investigating/fixing/reporting!
I don't know if it's related to the cache, because 24 hours later it's still shown in hovercards (for example, in page en:Si, if you hover over the link for en:International System of Units, which correctly skips the first hatnote ""SI" redirects here. For other uses, see SI (disambiguation).", but shows the outline hatnote "For a topical guide to this subject, see Outline of the metric system.", instead of the lead sentence "The International System of Units (French: Système International d'Unités, SI) is the modern form of the metric system and is the world's most widely used system of measurement, used in both commerce and science. ")
Furthermore, I also fixed a hatnote that was not using any template (and thus the hovercard showed "For related shorter-term variations, see Fluctuations in the length of day.") by intro with the en:Template:For and the hovercard showed immediately the correct lead sentence after that ("ΔT, Delta T, delta-T, deltaT, or DT is the time difference obtained by subtracting Universal Time (UT) from Terrestrial Time (TT): ΔT=TT−UT."), instead of the raw hatnote. So may not be related with the caches, and either something else must be done with the hatnote style in en:Template:Outline or Hovercards code. Hope this helps...
I checked again today and the hovercard now shows the lead sentence, instead of the text of the Outline hatnote. Cheers