Manufacturing a board with mixed 0603 and 0402 parts.
The 0402 capacitors place fine - although I need to use vision system on them.
0402 resistors have a curious problem. Because I sort my parts by feeder to place them, all parts in a certain feeder (I'll call is W20) are placed at one time. If two 0402 resistors are placed, they work fine. However if only one part, or three parts are placed on each board, then one 0401 part is left on the paper transport tape, uncovered.

The shockwave from from any feeder within about two feeders of the 0402 will "launch" the 0402 out of its pocket, and then the part cannot be located. So the machine has cycle back to re-place the part. The parts aren't expensive but the failed placements slow everything down.

So for 0402 why not:
Trigger the feed - 4mm advance with two parts.
Walk the tape back only 2mm on the first 0402 placement, and another 2mm (uncoverning the part for the) second placement?
Has this been tried? It seems really obvious - but maybe it was not easy to make this work dependably in practice.

Any workarounds for this situation? My east side feeders seem "gentler" somehow, and don't create as large a shock wave as the west side feeders.

My machine doesn't have needle valves, I'm looking forward to getting some and maybe solving the problem that way.

I already tried increasing the smaller top spring, we can try increasing the longer spring, its easy to do.

We are already using 300 ms on pickup delay - but longer isn't going to do anything if the part is no longer in the tape pocket where it's supposed to be. Again we don't have issues when we place even numbers of parts - only when "single" part is left on the machine (with no tape) and bounces out of the pocket from nearby feeders.

Isolating the feeder helps somewhat. The problem would go away completely if I didn't feed any feeders within about 8 or 10 feeders from the 0402 - but this is impractical. Also the problem would go away if I always placed even numbers of 0402 parts at one time, which is also impractical.