I use the 138079 flexible shoe in most of my loks. You can bend down the 2 brown copper parts to give the shoe more force on the studs for better pick up. Adjust the curvature of flexible shoe and check that it is flat when the lok is placed on the track.

For older loks that use a screw to hold the shoe on the lok, unscrew the shoe and use a fine screw driver to bend the 4 small tabs to remove the non-flexible shoe. The flexible shoe can then be used to replace the solid pickup shoes. They typically have the 4 tabs in the same locations.

Also, with light, non-heavy loks, I try to add lead weights into the lok, so the wheels will have better contact to the rails.

If you have a coach/car with taillights or interior lights, you can slowly roll it along the track to detect the spots where there may be an issue.
This could be due to a track issue where the metal plate that includes the studs has been pushed out of place and one or two of the studs no longer protrude to the proper distance.
If this is the case, you can usually press on the underside of the track section until it pops back into place. Normally this kind of problem can be detected by viewing the underside of the track section with a magnifying lens.

It is also possible that due to changes in incline/decline that there may be a spot where the slider cannot maintain contact with the studs. Are the affected sections flat or is there a slope?

It is also possible that a longer or shorter slider may yield better contact.

Check your track to make sure that the studs are not dirty and also check to see that there is no issue affecting the return via the rails as dirty wheels or track can also result in poor performance and loss of contact.
I would also recommend that you check how the ground (return) is wired/connected on the locomotive. Some models use the chassis (frame) as ground. Others may be isolated and use a metal wheel contact to provide electric flow. Such contacts can be affected by dust or oil residue.

One other suggestion that I can make is to swap out problematic track sections to see if the issue moves with the track. You can also try installing that track section in the opposite direction and see what happens.

Regards

Mike C

You mentioned your K tracks are new.
Are they the 2200 series and not the older 2100 series ?

Hello,

I completely understand your problem -- this happens mostly between turnout tracks and regular tracks. It's the normal dip (i.e., track geometry) that creates this problem. Most locomotives with newer sliders don't have an issue, but then there are those with older sliders that stall. That's one of the reasons that all my locos now have "stay alives" -- solves this annoyance.

Cheers,
Andry