If you create a new card by highlighting a word and clicking the + icon on the menu bar. The word in question becomes bold and purple to show that it is linked to a card. Then when you click that word it opens the card it is linked to.
If you then delete that new card, in an open session of scrintal, the bold purple styling remains on the word on the original card and when you click it, you get a message saying the card has been deleted.
If you quit scrintal and then re-open it (Mac M1), then the purple and bold styling still remains on the word that you had created a card from although when you click on it nothing happens.
I suggest as soon as a card is deleted any link and formatting that was applied to the linking word from the previous card, should be removed, as that word is no longer linked to a card.