Global variable is cleared after reboot

Software version: …
SW3.12
Robot generation: …
UR3
Steps to reproduce:

  1. First step
    Input “GO-HOME” to variable “global_var1”
  2. Second step…
    System reboot

Expected behavior:
Value of global string variable is keep after system reboot

Actual behavior:
Global string variable is cleared after system reboot.
Perhaps I think the cause is that it contains hyphen.