On some boilers from Bosch/Junkers/Buderus/Worcester changing a temperature only works if the rotary dials are set to AUT. Switching on/off is not possible, also set by the knobs.
On other controllers it is possible to send temperatures lower than the controller setting, but not higher. Some completely electronic settable controllers allow to change all values.
A new idea from a recent discussion and test: device-ID 0x12 is normally an alarm module that allows setting the flowtemp by a analog input. Try to set ems-esp to id 0x12 in the Settings and then try changing selflowtemp and selburnpow.
See the issue on Github.