Can you trip a breaker from a different circuit?
I can't figure out the problem yet.  Here's what I do know. And I have to save it because I can't visit chat without losing this. 

So even though this isn't an answer answer, I find when troubleshooting problem A, if there are unresolved issues B, C and D out there also, they complicate things in unexpected ways, making it much more difficult to be sure where the problem is.  

The old junction box MUST remain

It is not legal to remove that junction box.  You are required to make all splices inside junction boxes, and cannot bury them inside walls (splices or junction boxes). Every junction box cover must be reachable without use of tools of any kind. You can make your extension splices inside the box, whether it has a blank cover or a receptacle.  

It can have a blank cover, unless...

You need a receptacle within 6' of any point on a wall

You need to follow this wall its entire length between thresholds, (including around corners) and make sure there is still an outlet within 6' of every point along the wall.   So, within 6' of a threshold and every 12' thereafter.   This rule is because standard lamps and appliances have 6' cords, and you need to be able to route the cord hugging the wall (no cutting corners). 

If you didn't have that situation before, the old situation may be grandfathered (legal now since it was legal when installed or modified). The rule with grandfathering is you can't make things worse.  So if any area of the wall lost coverage because of the move, then you need to retain the receptacle at the old position.  (You can still have the new one). 

Mechanical execution of work

The lower picture looks perfectly proper. Wires must be 6" long past the cable clamp, and stick out 3" beyond the wall surface; don't get any shorter than that.  

2 circuits or not?

If the first photo is of your actual box, it indicates that all wires are feeding the same socket of the receptacle.  That means we can exclude "2 circuits" or "split switched outlet".  For sure, the two blacks in the old photo are spliced to each other via the outlet.  Ditto the two whites.  

This means only one circuit is in play (assuming there are not wiring defects elsewhere) and you only needed one cable, not two, to extend this circuit.  The other cable is superfluous.  At the old box, all blacks can be joined at the old box with a wire nut, and all whites ditto.  That will also reduce wire fill count to a sensible number.  

If you need a receptacle at the old box, either avoid using the receptacle as a splice and use a pigtail to attach to the receptacle.  Or use a "screw-to-clamp" type receptacle which gives four wire points per side.   Do not use backstabs (as in first picture), because backstabs cause nuisance problems, with opens or arc faults; but also, backstabs can't work with 12 AWG wire, which is your yellow cable there.  

The box must be large enough

For instance it appears your old box will have 


four 14 AWG wires (judging by the backstabs) which take 2.00 cubic inches each
four 12 AWG wires, 2.25 c.i. Each
Pigtails are free
a bunch of grounds (which count as 1 of the largest wire) so 2.25 c.i.
cable clamps (which count as 1 of the largest wire) so 2.25 c.i.
if you have a receptacle, 2 of the largest wire connected to it.  (4.50 c.i. If yellow jacket #12 wire is involved, otherwise 4.00 if using #14 pigtails.


If you need more cubic inches, before grabbing the claw bar, google "surface conduit starter box".  It's for launching surface conduit out of a flushmount box, but if you only use it for cubic inches, I won't tell :)