I think Opentherm can be very hit or miss due to the “standard” not being particularly standardised amongst boiler manufacturers. I would second @JohnMo suggestion and try running wiser in on/off mode, at the end of the day heating is about comfort not necessarily about running the latest flavour of heating control.
BTW I forgot when posting my comment that you were running OT, in that case I would expect Wiser to be constantly firing the boiler and the cycling periods to only be relevant to on/off mode.