AP Holds Max Total Amount. Sum of invoice and exchange rate variances exceeds limit

Hi

We have an Invocie for 11.70 GBP that went on Max Total Amount Hold. We are trying to understand why. The PO rasied was for 60,000 and 59997 has been match to the Invocie(including the 11.70) so the PO hasn't been overbilled

The Functional Curreny for this Organisation is EUR so the PO was rasied in MAR-2014 at exchange rate 1.2122520676279 and the Invocie for 11.70 was rasied in MAR-15 with exchange rate 1.36678109321363. Can someone explain the possibilties of why this invoice went on Hold? If it is to do with exchange would a Max Rate Hold also not apply?

Thank you for your help