HA2NON
First try to turn off Half Deviation in your transceiver (not DN mode - search for Half Deviation in the transceiver's menu). If you've found it and turned it off, use plain C4FM modem mode in the openSPOT.
If you can't find the Half Deviation setting, then it means that the transceiver will only support C4FM Half Deviation modem mode in the openSPOT. Run C4FM Half Deviation AutoCal.