Data Flash wrong reading issue

I am using rx631 series mcu. I have an application which uses data flash. If I program the mcu with application mot file. There is no problem. But If I erase code flash with Renesas Flash programmer. Some wierd things happen. After Erasing code flash, if I read data flash. Data flash memory have wierd datas. Some of them matchs with my data which writen while programming. If I read data flash again and again it changes everytime. Why is this happening ?

 

Thanks in advance.

Best Regards.

Emin ATEŞ