When applying an IPS policy you see a policy translation error in the console:
Policy Translation Failed: In sym_win_prot_os_bcd; file; <map rset="writeable_rs">: Variable not found: %exempt_user_list%
The policy can't be applied because the list "exempt_user_list" was removed from the policy and there is still a reference to the list in the sym_win_prot_os_bcd sandbox.
In the java console edit the policy revision you are attempting to apply
Use the search feature in the top right corner to search for the variable referenced in the translation error
Delete entries containing the variable
Save the updated policy then re-apply it