Dropouts from multiple cloned vocal tracks

You should not have to clone your vocals 4 times unless you are vocal layering. You should watch some videos on vocal eq, compression, and vocal strip.

they're probably cancelling each other out. Don't duplicate vocal tracks. That's not how you properly double and thicken. 

I recommend actually singing the same part 3 times across three different tracks. 

Primary track: Centered: full body
secondary: mostly hard left: eq out the bottom, small high mid boost with a high mid cut (like sine shape), possible cut highs
tertiary: mostly hard right: eq out the bottom, inverse high mid boost and cuts from your second track. 

The vocal strip has a decent doubler as well. I'd probably put a little bit of that in your main track, maybe a touch in your side tracks as well as a really quick, fast decaying delay. 

Just my 2 cents. This is more of a pop thickener. It's what I do. not sure if it'll fit for you, but that's my technique.

The key is to have TIGHT double and triples. If they aren't tight, splice em up and nudge them to be tight. You don't want a sloppy double. Anyone can do that and it sounds just that... sloppy.

Thanks for all the good feedback.  Phase cancellation indeed makes sense as the correct diagnosis.  Maybe the waves take a while to get set up in order to cause it in this case.

I seem to have eliminated the problem by reducing the vocal tracks to 3, and changing one of the presets.  Takes a while to do the trial and error since it's necessary to start from the beginning with each tested variation.

"Not so skilled singer" would certainly describe me, and this method was my "invention."  Nice to know it's got a name!  I'll have to work on the routine described by Josh and see if I can get the tracks in timing sync (on another song).

I am not trying to put together an artist recording, just a demo that I can play to get feedback on the song before probably opting for a pro demo.  I'm a songwriter only, and am able to get critiques at a couple of local workshops that we have in the Los Angeles area.

Thanks again.........Don

I'll have to work on the routine described by Josh and see if I can get the tracks in timing sync (on another song). 
   

Key pad nudges are your friend. I turn on mouse targeting ('x' key) and have manually set my keypad nudge 1 to something very small like 10ms.  I splice get the timing perfect on the main vocal and then splice up the filler vocals (alt+click on x1 makes it nice and easy) and then nudge them in reference to the main vocal. 

It takes getting use to, but I've gotten to the point where I can zoom in and visually nudge and be 99% perfect just by looking at it. The main thing to make sure is that you don't want to make it so they all start at the EXACT same point. You want it to be tight, but still be a thick double. 

Not the most fun part of being a producer / engineer, but the final product rocks. You'd be surprised at how much timing you can fix even though you're not a great singer. 

But as all things, really practice on your vocal accuracy and timing. It makes engineers happy =).

Cheers