Fast and easy was done the first time, incorrectly.

The sheets need to be lifted and spaced. That's the only way to eliminate future buckling.

Michael

Quick and dirty.

A 4"x6" piece of 1/2" plywood fastened with 1" screws in the center of the abutting plywood to take the place of the clips.

The clips are used to get a preset space between the panels for expansion. Just take a power saw, set the depth to whatever thickness plywood you have and run the saw along the seams. The spacing should be about 1/8", coincidently, the width of a saw blade.
You guys are trying to reinvent the wheel.
Ron

Clips are primarily for load transfer. They minimize the springiness on the sheathing seams when truss of rafter spacing is towards the far end of allowable spacing.

Normally used when trusses of rafters are spaced 24" or greater. The clip needs to be centered between the rafters or trusses.

As BusDriver noted, by holding the panel edges together, they prevent them from floating independently and causing seam lines in the shingles.

Gapping the panels? A byproduct of using the clips.

Retrofit? Yeah, blocking could be installed. You can do what the previous poster wrote, or if you have a helper to hold the blocking underneath, you can use longer screws and screw from on top of the roof deck down into the attic. That would give the threads better purchase.

You could also use small thin gauge metal plates, screwed from the top.

If you drill holes, you'll still have to use a small saw, something like a keyhole/drywall saw, to cut a kerf between the sheets that the clip can slide horizontally in to.

Not a fun remedy, whichever way you go.

But bravo for trying to make it better.

best,

Mongo