Already scrolled thorugh this forum and read the FAQs, didn´t find anything like the issue I´m having right now: I imported two decks from a friend of mine, which cards look perfectly fine in the preview while editing them (what they should look like and how they look like at her pc):
But if the “Basic (type in the answer)” note type was used to create this card (the note type will be in the title of the card template window, e.g. Card Types for Basic), it might be better to also rename the note type or instead change its note type back to the “Basic” note type using the card browser to avoid confusion in the future when you add your own cards with the same note type.
Maybe also try to import both decks into a new Anki profile (File > Switch Profile) and if they look good, copy the front/back template and the styling section (using the text editor) into the same note type in the main Anki profile to fix it.