Nahh, I wouldn’t start by blaming things that are poorly-understood or poorly-understandable on “bugs” and “departed people.”
What we need, in the OP, is a blend file, and maybe a screen-shot that illustrates the actual problem, and a more detailed description of what is actually wanted. I’m quite sure that others will then very quickly provide a bug-free way to do it that actually works.
You can, for example, animate the “influence” of a constraint, e.g. snapping it from 1.0 to 0.0 in two adjacent keyframes. (You can “animate anything™” in Blender now …) So, you can switch-off a constraint. (Although you can have sudden-motion of things when you do.)
One thing that I often do is to shoot two different shots, in two different scenes from the same camera POV, and cut them together such that the splice between them is visually seamless. I have actually dealt with the problem, then, in two entirely different ways at two entirely different times. In the finished product, no one will ever know. Editing is the “secret sauce” in an awful lot of effects . . .