Gas circulated hot water heating system problem?

Lennox gas hot water furnace series Q90-100, model GWB9 100IH, Honeywell L6006A aquastat, & S-9301A integrated boiler control. Weird problem, unit starts normally, purges, heats igniter, fires up perfectly, then after around 2 minutes goes on-off-on-off rapidly about 2-5 times, then shuts off, then purges, heats, fires up again like nothing happened. Does this repeatedly. When/if aquastat threshold is reached (180F), it shuts off normally and waits for it too cool until the differential point is reached before restarting. I measured the voltage at the gas valve input when the "on-off" thing is occurring and the voltage (24vac) is actually going on-off (like the S-9301A, for some reason, is "telling" it to do this). I opened it up and checked the circuit board for cracks, bad solder joints, burnt up parts, sockets & connectors & wires for bad/loose/corroded connections etc, nothing obvious. There are two bimetallic disk temperature sensors, one on the boiler casing itself which is a manual re-set and one on the blower casing, both seem to be OK. Anyway, what I am trying to find out is, is this a symptom of a bad boiler control? (This is an expensive part and I don't want to buy it and find out it was something else).

PS sorry about the "long story"