Blodgett (Zephaire-G) gas oven ignition problem, need advice.

Hi, my family run a small bakery in Ireland and over the past year our primary oven has had an intermittent fault. The problem seems to be that the pilot light does not receive gas. The oven usually starts fine from cold but once at temperature it often fails to relight. 
We have talked to every technician we could find in Ireland but to no avail, to be fair they all seemed fairly clueless and were not very interested. If anyone knows where I could in touch with people who are familiar with commercial oven I would be extremely grateful. 

Thanks, Adam.