I received a nice email from Agnès who created the CustomList function. I have copied her email below. The function has been updated.
“I just did the test and saw that the function Evaluate () is the problem ( the same for FileMaker Go )
it is the current limit of FileMaker Serveur internal Evaluate function
FileMaker GO Evaluate () is limited to 400 (+/-)
FMServeur Evaluate () is limited to 300 (test FMServeur v11 )
instead of 1700 (+/-) for FileMaker. ( runtime and IWP )
Do not hesitate to let me know by email if you have a problem with CustomList ()
In this case, I have made test with FMS v11, maybe the limit is different with other versions.
Be careful when using the CustomList custom function on FileMaker server. My testing has revealed that the list this function will generate is limited to 300 entries when used on FileMaker Server. The documentation of this functions states that it is limited to 500,000 on FileMaker Pro and 150,000 on FileMaker Go.