Data Migration Error

I am migrating a CE 1.9.4.1 site to CE 2.3.5 and have installed the data migration tool. All the integrity checks complete with no errors (including the EAV Step) but I get the following error:

In ErrorHandler.php line 61:

[Exception]
Notice: Undefined offset: 21 in /vendor/magento/data-migration-tool/src/Migration/Step/Eav/Data.php on line 492

Exception trace:
  at /vendor/magento/framework/App/ErrorHandler.php:61
 MagentoFrameworkAppErrorHandler->handler() at /vendor/magento/data-migration-tool/src/Migration/Step/Eav/Data.php:492
 MigrationStepEavData->migrateCustomEntityAttributes() at /vendor/magento/data-migration-tool/src/Migration/Step/Eav/Data.php:183
 MigrationStepEavData->perform() at /vendor/magento/data-migration-tool/src/Migration/Mode/AbstractMode.php:82
 MigrationModeAbstractMode->runStage() at /vendor/magento/data-migration-tool/src/Migration/Mode/Data.php:124
 MigrationModeData->runData() at /vendor/magento/data-migration-tool/src/Migration/Mode/Data.php:69
 MigrationModeData->run() at /vendor/magento/data-migration-tool/src/Migration/Console/MigrateDataCommand.php:59
 MigrationConsoleMigrateDataCommand->execute() at /vendor/symfony/console/Command/Command.php:255
 SymfonyComponentConsoleCommandCommand->run() at /vendor/magento/framework/Interception/Interceptor.php:58
 MigrationConsoleMigrateDataCommandInterceptor->___callParent() at /vendor/magento/framework/Interception/Interceptor.php:138
 MigrationConsoleMigrateDataCommandInterceptor->MagentoFrameworkInterception{closure}() at /vendor/magento/framework/Interception/Interceptor.php:153
 MigrationConsoleMigrateDataCommandInterceptor->___callPlugins() at /generated/code/Migration/Console/MigrateDataCommand/Interceptor.php:104
 MigrationConsoleMigrateDataCommandInterceptor->run() at /vendor/symfony/console/Application.php:1001

I have search for solutions and nothing seems to work to get me past this error.