Once each month with the Moon, and late each year for the other planets in all charts (horary or otherwise), there are two jarring ingresses to be aware of:
1) The Libra to Scorpio Ingress. Moving from the Lesser Benefic of Venus to the harsh, uncompromising intensity of the KBO Pluto = OUCH! Especially since the door from Libra to Scorpio is right at the Via Combust midpoint. (The Via Combust Way is from 15 degrees Libra to 15 degrees Scorpio.)
2) The Sagittarius to Capricorn Ingress. This ingress is about moving from the Great Benefic of Jupiter to the Great Malefic of Saturn. Talk about a sobering cup of coffee as good-time Sadge smacks right into the brick wall of reality of Capricorn.
The drop-off/whipsaw shift in dynamics is the same regardless of the planet making the ingress. For example, Mercury moving out of its Sagittarius detriment of unrealistic expectations and overly-optimistic thinking meets cold, hard reality in Capricorn, which requires a return to the drawing board to start over with diminished expectations or a complete change in plan. This is further compounded because 0 degrees Capricorn is a critical degree.
A querent I know had a few employment interview event charts with Venus in the later degrees of Libra as the significator of the potential employer (chart forthcoming). The employer wooed and wined and dined the querent, telling him how wonderful the company and location were, and how great the work environment was. The querent accepted the position, and by the time he began his first day of work, Venus had slipped into Scorpio. The employer promptly revealed what a financial mess the company was in, and told him flat-out, “I hired you to fix it.” Talk about the crumbling mess behind the pretty façade!
So give your querents a strong heads-up that dangerous curves are ahead (within the context of the chart) when these ingresses appear. Aspects and dispositors will determine whether the changes are for the best or not.