I sort this out on every substation job we do, and I treat signal, reference and shield as three separate conductors.
Signal: A and B on the twisted pair.
Reference: RS-485 needs a common mode reference. Add a third conductor (use a 2-pair cable, the second pair for 0 V) and connect the 0 V of every transceiver to it. Without it, the ground difference between the panel and a meter 140 m away eats into the receiver’s common-mode range, and VFD noise does the rest.
Shield: to protective earth, at the panel end, with a 360° clamp where the cable enters the cabinet, not a pigtail to a terminal. At the meter end either leave it open or connect it to earth through a 10 nF capacitor, which gives you HF shielding without a low-frequency ground loop. Both ends hard-bonded is fine only where the earthing system is meshed and equipotential, which next to a tray of VFD cables you shouldn’t assume.
Also check: 120 Ω at both ends of the line only, bias resistors once at the gateway, the tray separation from VFD cables (cross at 90° if you must), and no star wiring.
For the write-up, it helps to log the error rate. Have the gateway count CRC errors and timeouts per poll cycle and send them as telemetry, e.g. mb.crc_err and mb.timeouts, so you can show the before/after on a chart.