Minimum Pricing / Business Pricing

I’m having real issues with Minimum Pricing and hoping somebody can help. I’m trying to put some temporary sales on a few product lines - reducing price approx 50%. However, I’m getting 17001 and 17003 for every one of them - no matter the size of discount I try to offer (large or small).
“Please review your selling price and minimum price and ensure that your minimum price is less than or equal to your selling price.”

I’ve never had this issue before and cannot find a way to resolve it. The issue probably stems from me setting up Business Pricing a couple of weeks ago (small discounts across our full range). As part of that, in the Automate Pricing section there was this field which had to have a number entered:
“Set Minimum price % for existing SKUs where no Minimum price has been set previously and for newly added SKUs. Required”
I set it at 51% - assuming this would allow us to drop the prices for sales etc, but I don’t really know.

Would really appreciate some help as Seller Support are f***g useless as expected.