Ender 5: Bowden tube shifts in/out of extruder during retractions I have an Ender 5 with an aluminum extruder that was printing beautifully for a few days after building it. I received a Capricorn bowden tube and new couplings as a gift, and replaced those, and now I have stringing issues I can't solve. 

I've been all over the map with settings (temps, speeds, z-hop, retraction, etc. etc.), I've swapped the tubes, the couplings, the filament, I've checked for clogs, and put clamps on the collars, but no matter what I do, the tube shifts in and out during retractions by about .25 - .5 mm. I suspect that has something to do with the stringing, as nothing else has solved it. 

Any suggestions are appreciated. I haven't made adjustments to the extruder, but I don't know if that's possible or necessary. I've never had a system using the bowden, so that part of 3d printing is new to me. I'm using 3d Solutech PLA.
If it's just the pressure fitting on the brass coupler that shifts in/out, or the PTFE tube shifting slightly in/out but remaining in the coupler, that shouldn't be a problem unless it's so loose it can come out entirely. The blue clips which should have come with the printer are intended to stop this motion or at least provide enough pressure to prevent it from falling all the way out.

Regarding the small 0.25 - 0.5 mm of play, effectively it just means you lose that much length from your retractions, since part of the retraction goes into pulling the tube back into the coupler. When the retraction is reversed, the effective filament position should go back to what it was before the retraction. As long as your retraction amount is sufficient after the loss, it should not cause stringing.

You probably need to look for another cause of your stringing.