How to Avoid Problems with Rapido Couplers?

[RowanMackenzie]

I've heard mixed things about these, but using them is kind of unavoidable for me. So far I've only had a couple of bits of rolling stock that have had problems, their couplers don't seem to go down all the way, thus they slip loose easily. Anyone know of a way to combat this?

[Byegad]

If you talking about Peco wagons, the droop you mention is due to the nut at that end of the wagon needing nipping up. Remove the wheels at that end and depending on the amount it droops by anything from a 1/4 to a turn and a half, may be needed. The Peco version of the coupler is prone to this, but the sprung ones, on older pre-NEM, stock from many manufacturers, can droop due to a weak spring or bad seating of the shoulder. They're easy enough to replace once you work out the way to disassemble the mount. Some merely twist out, others have a keeper plate.
Additionally Tacky Wax helps keep things together on lumpy track.