DTMF Relapce Tran not working correctly

Dear Support,

I have a problem:
If enable "DTMF Replace Tran" and DSS (MEMO) key in BLF mode, phone send only "Trans Send DTMF" code.

Settings:

DTMF Replace Tran: enabled
Tran Send DTMF: ##

Memory or Line key 1:
Type: BLF
Value: 302
Line: Line 1
Extension:

Memory or Line key 2:
Type: BLF
Value: 303
Line: Line 1
Extension:

If I press any Memory button, phone send ## (Tran Send DTMF). Missing the extension number.
I tested several phone type (T23, T26, T27, T28) All operate same way.
(The BLF workink correctly)

What could be the problem?

Thank You
Istvan