I installed the registration module version 1.2 on OpenMRS 1.6.3, generated identifiers but was unable to upload these identifiers. When I changed global properties to allow manual entry of identifiers and created records, I discovered that the records were never created. I didn’t get any error.
Unfortunately OpenMRS (now Platform) 1.6.x has been unsupported since 2012. Are you able to reproduce this error on a more recent release such as Platform 1.11.x?