Highlead GC-0618-1sc taking two steps forward, one step back at narrow section

[Rylando]

My highlead GC-0618-1SC is having an issue I'll describe as two steps forward one step backwards. When I get to a narrow section of a piece of leather, when the machine goes to walk the leather, it doesn't work quite right and seems to back it up a little bit before going forward and making the next needle hole. It only seems to happen on a narrow section where the leather probably isn't touching the needle plate underneath. 

The first picture is the underside of the stitch, where it suddenly starts looping on the bottom. The only reason why I can figure it does this, is because the leather doesn't touch the needle plate. Is that the right idea or am I going in the wrong direction? Could this be a tension problem or a mis-adjusted machine?

The second picture shows the underside where it sews perfectly and no loops, and the third shows how it loops where it goes to a thin section. 

Any suggestions on whats happening here and/or how to fix this?

 

[Rylando]

Forgot to mention: The above pictures are with #138 thread and a size 21 needle. 

However, I get just fine results with #69 thread and a size 18 needle. 

[Wizcrafts]

1 minute ago, Rylando said:

The above pictures are with #138 thread and a size 21 needle.

That is the wrong size needle for #138 thread. You should use at least a #22, if not a #23 leather point needle.

[Rylando]

8 minutes ago, Wizcrafts said:

That is the wrong size needle for #138 thread. You should use at least a #22, if not a #23 leather point needle.

Ah! Maybe that was my problem. Will go bigger needle and try again soon.

I should know better than to trust the first result for me on google https://www.servicethread.com/blog/industrial-sewing-thread-needle-sizes

[Wizcrafts]

4 hours ago, Rylando said:

Ah! Maybe that was my problem. Will go bigger needle and try again soon.

I should know better than to trust the first result for me on google https://www.servicethread.com/blog/industrial-sewing-thread-needle-sizes

Right! Try this chart instead: https://www.tolindsewmach.com/thread-chart.html

I usually choose the largest recommended needle when I sew medium to hard temper leather. It needs wider diameter holes to overcome the friction.