Strangly enough I had the same issue with another project and fixed it by getting rid of the power capacitor.
If you have a routine that's writing to EEPROM, and a large value cap on the power rail, it
may still have enough time to write to EEPROM before the cap discharges after removing
power.

Or, are you saying, you get writes on power down without any routine in your code that
writes to EEPROM?

the WREN I dont really understand
WREN is a bit in EECON1, that, when set, allows writes to Flash program or data EEPROM.

Normally this bit will be set at the start of an EEPROM write routine, and then cleared once
the write is complete.