I know this is several months old but I know how frustrating it is to find a thread that you think will solve your issue only to find it trails off with no answer!!

So, just a quick update. JetCat confirmed that my supposition of there being an internal blockage was correct. They suggested I apply 120-150PSI to the 3mm festo line and 'blow out' any blockage. Gave it a go and nothing obvious happened - just took compressor up to about 140PSI.

Tried a start and it started instantly. Never an issue since.

So there you go [8D]

Cheers,
Mark