I've read through the references to Hazardous Movement acts listed in the Index, and it appears that Crew Survival (D5.6) is a unique case. The wording of D6.5 states "is subject to the effects of Hazardous Movement... vs all subsequent attacks during that phase." That can be read as varying from A4.62 "incur a -2 IFT DRM to any attacks against units so engaged regardless of fire phase until they are pinned (if subject to Pin results)." The difference is that Haz. Move. only applies during the phase the CS occurs; however, as Klas notes "the basics of Haz. Mvt" is not modified.
The interpretation of A4.62 rests on whether "until pinned" is a final or temporary condition, ending if the pinned unit breaks. Other acts of Hazardous Movement (clearance, pushing; fording and parachuting are NA due to immunity from Pin) can result in a unit pinning and then breaking; does the unit engaged in that act resume the act after a pin - break sequence? There are very few instances in ASL where a status can thus end and then resume, so it seems inconsistent that Hazardous Movement can cease (when a unit pins) and then resume when the pinned unit breaks.
If so, then: a squad pushing a gun is attacked and pinned; Hazardous Movement no longer applies. The squad is attacked immediately thereafter and breaks, and thus resume pushing since that act is required to qualify for Hazardous Movement.
The phrase reads "until pinned" and not "unless pinned" - thus Hazardous Movement no longer applies once the Pin occurs, and does not resume when the Pin status ends.