Problem with PO InfoUpdate. PB00 + RL01 becomes new PB00

Hi

We are trying har to implement the correct use of conditions on Vendor / Sub-Vendor / PO and so on.

But we have one problem.

We have added condition RL01 with the value of 20% discount on Sub-Vendor "NDP"

The Info Record for Material X and Vendor X has the following info:

PB00 = 1000 USD (validity to 9999-99-99)

SUB-Vendor = NDP

So when new PO is created we get 1000 USD - 20% = 800 USD is the net price - so far so good.

The InfoUpdate indicator is ticked by default and we save the PO.

Next time we do a new PO the PB00 has changed to 800 USD and the RL01 is still -20% giving us a new net price of 640.

And this becomes and endless loop where the gross price - vendor discount becomes the new gross price on the next PO.

Any ideas?