Have you looked at the charge capacitor voltage to see what it is doing during the gap?

 

Those are just the values I calculated.

They're still not realistic. You can't expect to get nano second resolution, even with 1% resistors. The cap you're using is probably 10% at best. Plus 555 timer accuracy drifts with temperature.

I've never seen this with a 555 before and was thinking maybe it had something to do with the high value of the capacitor (i.e., 47uF) but this is me just completely guessing.

47uF isn't considered large.

Any ideas why it would do this every 6-7 cycles

Check the voltage on the timing capacitor and control pin when the gap happens.

 

Have you got a decoupling capacitor across the supply pins of the 555 ? It's not needed in the sim but it is in the real world.