Overview:
Sample Limits are not enforced. A user is able to drop samples that violate Sample Limits, even though Sample Limit Transaction records are created.
Root Cause:
The user is missing Field Level Security (FLS) Read permission to the Account_Types_vod__c field on the Sample_Limit_vod__c object.
Solution:
Grant the user Read permission to the Account_Types_vod__c field on the Sample_Limit_vod__c object.
Related Documentation:
CRM Help Documentation: Using Sample Limits