For the record, Today I have update HWN-4208MH using firmware NVR_K74_BL_ML_STD_V4.30.085_210409 
, from old buggy interface to new.
Fix ONVIF protocol to Chinese cameras.
PTZ OK
Alarm notification OK
All Things WORK.
NOT WORK:
UNBIND Recorder from other account.
SADP ERROR to UNBIND
Iphone APP , android app error to unbind
Only possible to remove device from https://ieu.hik-connect.com/users/page ( not tested to downgrade to old GUI and firmware to UNBIND)
Best regards
, from old buggy interface to new.Fix ONVIF protocol to Chinese cameras.
PTZ OK
Alarm notification OK
All Things WORK.
NOT WORK:
UNBIND Recorder from other account.
SADP ERROR to UNBIND
Iphone APP , android app error to unbind
Only possible to remove device from https://ieu.hik-connect.com/users/page ( not tested to downgrade to old GUI and firmware to UNBIND)
Best regards
