Boru Carrig Mor stove not heating radiators

Hello,

A problem with my Boru Carrig Mor 20/30kw stove in the past couple of days. I am hoping folks on the forum can provide some guidance.

In early Mid October I had the stove cleaned (annual clean) in preparation for regular use in the coming months. In the last 3 to 4 days, I have noticed that the stove isn't heating the majority of radiators in the house (I have 4 downstairs and 7 upstairs)

After checking just now, one radiator downstairs is lukewarm and five of the seven upstairs rads are lukewarm. Other than that all other rads are cold.

I also noticed a gurgling sound (trapped air?) emanating from the stove 15 minutes after lighting it.

Back in March/April When I had had the first lighting the rads would typically heat 15 minutes after lighting the first and having top and bottom vents open.

I should had that the thermostat associated with the stove is typically set between 30-40 degrees the pump does engage after lighting the fire (a i can hear it b) the upstairs rads are lukeworm).

There is also a one way twist-able value that appears to let out air, I gave this a couple of twists and i could hear air being released. I also note i did have one evening this week where all the rads did heat via the stove, but since Tues poor levels of heating.

I assume I will need to call someone to service the stove, but i would like to get additional background on the problem and possible solutions so as i don't appear totally clueless when speaking to a stove service person.

I should add that I also have oil fired central heating and the rads work fine (i.e all rads are heated via oil)

Thanks in advance for any replies.
Jonathan