Condition type doubled in item of an oppotunity

Hi experts,

we are facing a strange issue.

When creating an opportunity in CRM WEB UI,

after entered the product and quantity, the customer are requested to enter the "Entitled price"(YBPD).

The initial value of of "Entitled price" is 0. If I saved the opportunity without entering the  "Entitled price".

The attributes of condition type YBPD is like below:

If the user entered the value,20,for example,

the system add a new condition instead of changing the existing one.  Two YBPDs in the item condition list.

The normal one should have attribute value:

While the redundant one have attribute value:

Can anybody suggest what the problem is and how we can fix it?

Thanks.

Jerry.