Today I updated an existing model used by existing records.
I added two new boolean fields using the switch interface.
I then manually updated each of the records using this model - But, I only triggered the first of these on each of the records.
When querying all records for this model in the API explorer I noted that only the first of these was set to a boolean value true|false for each updated record - The second value was null and not false as expected.
I then edited each record and set the second boolean switch to ‘on’ so that it returned a ‘true’ result.
I then edited each record and set the second switch to ‘off’.
This finally returned false instead of null when using the API explorer to query the records.
I hope this explanation was helpful in reproducing the issue.