Here's what worked for me. After many hours of trial and error, this was extremely annoying, tedious, and time consuming, but it worked. I have asked Apple to continue to look for another possible solution as it shouldn't be this complicated!
It seemed to me that once a spreadsheet had the error message there was no way to remove the error message from that spreadsheet (ever). I went so far as to duplicate a spreadsheet that contained the error message and select all and hit delete. I then closed and reopened it, and the error was still there. If I created a blank new spreadsheet, it would not contain the error, but if I selected all from the old, copied and pasted into the new spreadsheet, the error would appear when opened. Here's how I proceeded;
1.First, create a blank new spreadsheet.
2. Open the spreasheet with the error.
3. Select one object only, copy and paste into the new blank spreadsheet.
4. Click "spreadsheets" in the top left corner and then reopen it.
5. If the error appears, delete the new spreadsheet and create a new blank sheet. If there is no error, go back to step 2 and repeat with a different object.
6. Go back to the sheet with the error, select the same object that you just copied. Under the table options, turn on table name, change the table font to anything, and then back to the font you wish to use. Turn off the table name again (unless you want to use it, which I didn't in the first place).
7.Copy the object again and paste into the new blank spreadsheet. Click "spreadsheets" in the top left to close and then reopen the sheet to check for the error. For me at this point the error was gone.
I had to do this for EVERY SINGLE opject in my spreadsheet. Each time you find an object with an error, you will have to delete the new one you made and create a new one that is error free. You don't have to start over and copy the objects that you previously copied.
8.Once you have dont this with EACH object and ensured that you can open the new spreadsheet and not get the error message, create a brand new spreadsheet again.
9. Go back to the original spreadsheet that you checked every object and changed the table font. Select All and copy.
10.Paste into the newly created spreadsheet. It should now be error free, even though the original still is error prone.
Repeat all the above steps for every sheet within each workbook, each time you complete checking every object on a given sheet, you can do steps 9 and 10 into the same worksheet that you created after finishing the first sheet.
When you are all done, rename the tabs in the new worksheet to match the original. Then delete the old worksheet (at at least change its name) and rename the new worksheet to the name of the orignal.
You should now have an exact copy of the old error prone worksheet in a new worksheet error free.
Like I said before, it was very time consuming and a tedious, annoying, PITA, but it worked! Each time you open the old error prone worksheet you get the message and have to click done. I hope this works for you in the meantime, while Apple works on a better fix. I'm hoping that my information here will help them discover what might be causing the problem so they can fix it on their end.
