Hi,
Sorry for the delayed answer.
Section 12.3.3 of the CC2510/11 User's Guide (SWRS055) covers this topic. On page 85 it says: "The flash erase operation requires that the instruction that starts the erase i.e. writing to FCTL.ERASE is followed by a NOP instruction as shown in the example code. Omitting the NOP instruction after the flash erase operation will lead to undefined behavior.".
Br,
ABO