Stanton Straight tonearm stylus sticks skips

I think with these designs, it's also the length of arm ie these are quite short where as proper hifi straight arms are longer and therefore give a better angle to record, if you see what I mean..... Can't really understand the design ethos of the Stanton arm really, other than it makes it less likely to catch the arm on your sleeve when scratching.

IIt's the drag on the needle that makes it skip forward, hence with other decks the anti scate pulls the arm back. Heavier bass or deeper grooves Will succumb to this issue. You cannot be be the only person having this problem. Wonder what DJ forums have to say.

Strange it's sticking rather than jumping forward tbh, does point to arm bearings as DS has suggested. If it's because of bad aliagnment, it'll be REALLY chewing the grooves just before and at the point of sticking. Be careful of you tunes.

i agree it should be returned, but I think there might be a clue with the difference in channels, maybe the wire going from the arm through the pivot might be tigh/trapped...... Doesn't sound like it's actually worth investigating though.
Is this deck for a reggae/ bass heavy soundsystem? Heavy deck with no big voids inside will cut down integral feedback issues, I used a lenco goldring for years before succumbing to sl1210.

Tbh, a heavy plynth is a good starting point. By voids I mean gaps inside. This implys thinly made plynth (what the TT is built into). The 1210 to me is good as it has a solid metal frame, surrounded by non resonant rubber which means the whole deck has no one resonant frequency. A large object like a deck will resonate at a fairly low frequency most often at a similar frequency to one note in a bass line hence it beginning to 'ring' at that frequency (or note). The larger the mass, the lower that may be, and the more energy required to make it resonate.
  So the goal is to find a deck that is heavy and dosnt have a particular note when you tap it with your finger with the needle sitting on a stationary record. Plastic decks, in my experience are very prone to ringing.

What I'm suggesting is that the wire going through the bearing might be the cause of the arm sticking and might have been stretched as to make a partial connection when the arm is moved. A long shot admittedly though. Sounds as if the deck is fundamentally flawed though due to the short arm design, so yeah, I'd sack it and get another. Generally, decks from the 70's were well built and heavy. 80's brought the horrible silver plastic crap...
Good luck