DX310 Dishlex Rinse Light Flashing but it is draining?

According to manual, flashing "Rinse" light means the machine is not draining. My Dishlex DX310SA is stopping during the initial cycle, "rinse" light flashing, but the machine is fully drained.

When you clear the machine and reset, the drain pump runs for a long time (dry), and then rinse light flashes again.
This repeats a few times until it eventually resets.

Have stripped and cleaned all fittings, filters and hoses, and drained hose directly outside to ensure no plumbing backfill issues.

So my quesion is...Is there a water level sensor arrangement to indicate the machine is drained? or could this be a more serious problem like a control card etc?

Keen to get some idea before calling out the repair man on hourly rates...