axle is not 'catching' on 10% or so of pulls - Model B

[creature]

I have a model B. getting worse now, about 10% of the time I pull, the pull doesn't engage flywheel*. the chain is not slipping - it is on tight and is spinning the axle*, but nothing happens. this causes a quick resistance free pull and sometimes i bonk myself in the chin with the handle as a result.

Anybody heard of this issue before and/or have a suggestion to fix it?

* it is possible I am not giving the correct names for these parts... but I think by my description you get the gist of what is happening... hopefully.

Thx.

[johnlvs2run]

How firm is the handle sitting against the cage at rest?

How many kilometers are on the rowing machine?

If the handle is firm, it's possible that the clutch is slipping, which usually doesn't happen until after 20 to 25 million meters. In case it is, then it either needs cleaning or replacement. I replaced mine, which wasn't that difficult, most of the work involving taking the cage apart. As the same time I replaced one of the sprockets with a 14 tooth so it would be the same as the CDE sprockets and the drag factors would have the same range of resistances.