Meter reading unit does not match rate category

Hi.

I have a case. I have installation with Rate category with Dynamic period control(DPC) and Meter reading unit with estimation.

I need to change this Rate category and put other with flate rate billing without DPC. But system shows error AJ677. According this I have to change Meter reading unit too (without estimation).

So quastion is. Is it possible to use one Meter reading unit for both Rate categoty (with DPC and without DPC)?