Cannot scroll above row 96 in Numbers

I've done something to my spreadsheet.

I am currently on:

and

I'm running older software because there are some 32-bit applications I use for which I have not found suitable 64-bit substitutes.

My spreadsheet file is sizable at 9MB and is currently saved as a package. In the main spreadsheet, I currently have 6340 rows and columns out to AJ with a few hidden columns. The first two rows are header rows. There are no header columns. There are a total of thirteen spreadsheet tabs. All the other spreadsheets (other than the main) are tiny by comparison. There are numerous links between three spreadsheets where formulas reference various cells between those three spreadsheets. All the others are just lists of data.

I've done something in my main spreadsheet such that I can't scroll above row 96. I can access the data if I search or use the arrow keys. I can see the information on the status line at the bottom. But I can't scroll up to row 3. 96 is the highest it will go. Adding/inserting empty rows and deleting rows with data (on the order of 10-20 rows) has no effect. I can go no higher than row 96. Selecting the lower header row and arrowing down to row 3 does not affect the scroll issue. I can't see what I've selected other than what shows in the status line at the bottom. I can actually enter and edit data, though it is somewhat problematic not seeing what I'm doing (again, other than the status line). If the first displayed row under the table header is some higher row number (like 350) and I arrow down from row 2 (the second table header row), no scrolling occurs. But I'm still in row 3. A search that points to a row between (and including) 3 and 95 does not scroll the spreadsheet. I can't see the result of the search unless I look in the status line.

Use "Dr. No" for an example search into the hidden rows. Arrow up and you will see the table header "Title" highlighted. Arrow down from "Dr. No" and you will see other titles, but no highlighting.

When I do a print preview of the main spreadsheet, the first page is missing the header rows. The first visible row is … if you guessed 96 you guessed wrong … row 90. And that first printable row is shown on the edge of the paper, so it won't actually print. The page header shows on the first page. The following pages do show the table header rows.

The behavior on my phone (iOS 14.6) is the same. I presume the spreadsheet loads in a later version of Numbers when I access it on my phone.

I'd like to know what I've done wrong; but more importantly, how to fix it … preferable without having to upgrade any software.