Is there a limit on the number of text boxes configured as links to pages on a page
There's a limit of 4 cards within 1 "row" of cards. 1 "row" is what you've done.
However, you can create a workaround, by creating multiple "rows", and there's a larger threshold of "rows" that you can create. Please note how i have created multiple "rows" of links below, and if "Navigation 2" has more links than "Navigation 1", you can add dummy cards under "Navigation 1", and make it invisible by unselecting "background" of the card.