Just feel the left hand pipe, if its hotter than the right hand one then the pump is pumping in the correct direction.
Also that left hand pipe should be coming off the top side of the boiler with the right hand one returning to the bottom of the boiler.
I have a SE 20kw Firebird with the pump on the return and if the boiler re fires after say 10/15 minutes after zone valves shut then re open you can hear the water burbling for a few seconds in the flow pipe, I have measured this temp at 90/100C (boiler SP 70C). Obviously if boiler just cycling normally then no problem as circ pump running continuously.
The recording might sound a little like cavitation so maybe reduce pump speed to 2 and/or if boiler SP temperature 70C or more reduce to say 65C.
You also said that the boiler cycles right from the start, from a cold start it should run continuously for 20 to 30 minutes until system contents up to temperature, presume yours does likewise.