Same issue here, although only with some pedals. Dura Ace 7400's basically have a tab that forces the bend in the strap so it stays in place. However, this was generally a problem with toe straps since the dawn of time -- old Campy Records and Superleggera's had the problem as well.

The biggest problem with Toshi's is the beefy lamination. I was helping a teammate with a pair of MKS's that had this problem and finally fitted the straps to identify the precise point where a bend was needed, then removed them, folded and dipped that point in some almost boiling water for about 15 seconds, and then immediately reinstalled them and tied them in position until they cooled. Whether it softened the plastic, the leather, or the glue holding them, it seemed to do the trick and hasn't caused any delamination with a lot of track riding for almost a year. You might try that and see if it helps.