Hi Pradeep,
I have faced this error in my last project.
I was using {E} that time when I got this error. I did further analysis and found that I get this error when I try to use MX_INACTIVE = {E} or MX_INACTIVE = {R} for users who did not have MX_INACTIVE = 1 set (we would expect that it's shouldn't matter as users do not have MX_INACTIVE set)
If the users already have MX_INACTIVE = 1, then it worked fine for me.
I used %% instead of operator but anyway you got other work around as you mentioned. I did not raise it with SAP as I had work around.
Kind regards,
Jai