AtD translation: and many began to edge away, anticipating trouble up the tracks

[Mike Jing]

P367.33-38   Yup Toy herself, waiting by a huge ice machine among a row of
Oriental ice-girls in abbreviated sequined getups, her painted face a
porcelain mask in the naphtha-light streaming from somewhere beneath,
gazed, sucking at a scarlet fingernail, failing to look inscrutable to any
but the habitually dismissive, such as Ruperta. To others more appreciative
of her virtues, her mind was an open book, and many began to edge away,
anticipating trouble up the tracks.

What is this last part of the sentence about? What kind of trouble is being
expected? And what is "up the tracks" exactly?