"choice" column in List not consistently displaying values

I created a sharepoint list from an Excel worksheet.  A few of the columns in Excel had a value of either "true" or blank; when creating the list I set those columns as "choice".

Initially, these columns displayed "true" (for the applicable rows) -- but sometimes the "true" value is not displayed.  It seems to change whenever I make a change to a different column.

For example:  I changed a different column to also be "choice"; all of the columns previously set as choice now displayed the values.  However, after I made another change (to not display a completely different column), the values were no longer showing.