Condition types disappearing in the sales order

Hello Team,

Please help me on this issue.

We have two condition types ex: ZAAA and ZBBB (both are difined with only for statistics) and assinged to pricing procedure with steps 180 and 182 .

Now the problem is when we create the sales order these both condition types and displaying in the sales order item condition types, but when the user changes the Tax clasifictiaon (which comes from the material master) from example V to 6 the above two conditions types are disappearing in the sales order.No routines is used.

could you please let us know where is the link between these condition types and tax clasification of the material, why these considition types are disappering, is there any configration setting is available for this?,Please help me.

Thanks & Regards,

MK.