Casatronic Timing / Strobe Gun Issue?

Sanity check required
I have watched the Casa video how to fit and time my casatronic ignition
I have marked my mag housing at 24 and 16 degrees BTDC, with the expectation at fast tickover I set the timing to 24, and then as revs rising the firing point advances to 16
I'm also aware with this ignition there are two sparks per revolution, 180 degrees apart
At fast tick-over my strobe indicates the mark on the flywheel correctly in relation to the 24 degree mark on the mag housing
However as revs rise, instead of the flywheel mark advancing towards 16, it completely vanishes !
The marking at 180 firing point remains visible at all times - the engine sounds clean still (indicating it must still be firing between 24/16 BTDC
anyone else seen this issue
This must mean my strobe is knackered - would you agree?

I have watched the Casa video how to fit and time my casatronic ignition
I have marked my mag housing at 24 and 16 degrees BTDC, with the expectation at fast tickover I set the timing to 24, and then as revs rising the firing point advances to 16
I'm also aware with this ignition there are two sparks per revolution, 180 degrees apart
At fast tick-over my strobe indicates the mark on the flywheel correctly in relation to the 24 degree mark on the mag housing
However as revs rise, instead of the flywheel mark advancing towards 16, it completely vanishes !
The marking at 180 firing point remains visible at all times - the engine sounds clean still (indicating it must still be firing between 24/16 BTDC
anyone else seen this issue
This must mean my strobe is knackered - would you agree?