New Post: static (clear) BDK?

We generate a BDK using BI command, and console shows:
 

Request: 1234BI;UU0
MAJOR>>>Parsing header and code of message 1234BI;UU0...
MAJOR>>>Searching for implementor of BI...
MAJOR>>>Found implementor ThalesSim.Core.HostCommands.BuildIn.GenerateBDK_BI, instantiating...
MINOR>>>=== [BI], starts 13:30:54.738 =======
MAJOR>>>Calling AcceptMessage()...
MINOR>>>[Key,Value]=[Delimiter,;]
[Key,Value]=[Key Scheme LMK,U]
[Key,Value]=[Reserved,U]
[Key,Value]=[Reserved 2,0]

MAJOR>>>Calling ConstructResponse()...
MINOR>>>New BDK (clear): EF3D7A252AA8EAF82919E6C4D99EC86B
MINOR>>>New BDK (LMK): U243095316AC1757907565118B441BB31
MAJOR>>>Calling ConstructResponseAfterOperationComplete()...
MAJOR>>>Attaching header/response code to response...
MAJOR>>>Sending: 1234BJ00U243095316AC1757907565118B441BB31
MINOR>>>=== [BI], ends 13:30:54.748 =======

 
In our implementation, we use this clear BDK in pin pad and an initial KSN to generate per device IPEK.

Pin pad sends 3DES encyrpted pinblock in Ansi9.8 ISO-0 to server with KSN, and we pass to Thales using command CI which translates successfully:

MAJOR>>>Calling AcceptMessage()...
MINOR>>>[Key,Value]=[Account Number,999999999999]
[Key,Value]=[BDK,243095316AC1757907565118B441BB31]
[Key,Value]=[BDK Scheme,U]
[Key,Value]=[Destination PIN Block Format Code,01]
[Key,Value]=[Encrypted Block,7C6E2C03F30AADBF]
[Key,Value]=[Key Serial Number,FFFF0123456789E00002]
[Key,Value]=[KSN Descriptor,605]
[Key,Value]=[ZPK,450CF23F70F182EB]

MAJOR>>>Calling ConstructResponse()...
MINOR>>>Clear source BDK: UEF3D7A252AA8EAF82919E6C4D99EC86B
MINOR>>>Clear target ZPK: 5E752CA43194A8F4
MINOR>>>Clear PIN Block: 04551E6666666666
MINOR>>>Clear PIN: 5587
MINOR>>>New clear PIN Block: 04551E6666666666
MINOR>>>New crypt PIN Block: 4A2D6BFA62BB9866
MAJOR>>>Calling ConstructResponseAfterOperationComplete()...
MAJOR>>>Attaching header/response code to response...
MAJOR>>>Sending: 0004CJ00044A2D6BFA62BB986601
MINOR>>>=== [CI], ends 13:31:46.154 =======

 
However, if we restart server calling BI again, it generates a new clear BDK and the translation of pin block fails:

MAJOR>>>Parsing header and code of message 0004CIU90AB1164E510816161D4D74C312A83C41CC5DB1D37156A0B605FFFF0123456789E000027C6E2C03F30AADBF01999999999999...
MAJOR>>>Searching for implementor of CI...
MAJOR>>>Found implementor ThalesSim.Core.HostCommands.BuildIn.TranslatePINFromDUKPTToZPK_CI, instantiating...
MINOR>>>=== [CI], starts 13:32:27.154 =======
MAJOR>>>Calling AcceptMessage()...
MINOR>>>[Key,Value]=[Account Number,999999999999]
[Key,Value]=[BDK,90AB1164E510816161D4D74C312A83C4]
[Key,Value]=[BDK Scheme,U]
[Key,Value]=[Destination PIN Block Format Code,01]
[Key,Value]=[Encrypted Block,7C6E2C03F30AADBF]
[Key,Value]=[Key Serial Number,FFFF0123456789E00002]
[Key,Value]=[KSN Descriptor,605]
[Key,Value]=[ZPK,1CC5DB1D37156A0B]

MAJOR>>>Calling ConstructResponse()...
MAJOR>>>Exception while processing message
System.ArgumentOutOfRangeException: Index and length must refer to a location within the string.
Parameter name: length
at System.String.InternalSubStringWithChecks(Int32 startIndex, Int32 length, Boolean fAlwaysCopy)
at ThalesSim.Core.PIN.PINBlockFormat.ToPIN(String PINBlock, String AccountNumber_Or_PaddingString, PIN_Block_Format Format) in C:\Users\Documents\ThalesSim.Src.0.9.6\ThalesCore\PIN\PINBlockFormat.vb:line 177
at ThalesSim.Core.HostCommands.BuildIn.TranslatePINFromDUKPTToZPK_CI.ConstructResponse() in C:\Users\Documents\ThalesSim.Src.0.9.6\ThalesCore\HostCommands\BuildIn\TranslatePINFromDUKTPToZPK_CI.vb:line 108
at ThalesSim.Core.ThalesMain.WCMessageArrived(WorkerClient sender, Byte[]& b, Int32 len) in C:\Users\Documents\ThalesSim.Src.0.9.6\ThalesCore\ThalesMain.vb:line 778
MAJOR>>>Disconnecting client.

 
Our work suggests pin pad is initialised with static clear BDK, and BSK should not change.

Why does the simulator create a new clear BDK each time, and does a production Thales HSM also demonstrate this behaviour? Or, is there a BDK under LMK that should be used for IPEK generation?

Many thanks!