This issue occurs because the limit for MAX_USER_FIELDS_SIZE is 2048. It is set by JSAgent and cannot be configured by user config. If you would like to add this much information into the userData field, the only workaround is to use short key names.
Note: To further isolate the issue, you can also check the dump log and search forUser event info field *** dropped because it is too long?***in the field's name. There are two numbers representing the actual size and the max size at the end of this message.