Importing Altium schematics to a PCB is placing some components on a forbidden and an unaccessible area
This is a combination of multiple errors, some user-based and some bugs in the SW.
The reason your components are imported quite far from their designator is a problem with your libraries. This is due to where the origin-point of your component is located. It should usually be in the center of the component (or on Pin 1). If it instead is somewhere in a corner, you'll see this effect.
In earlier versions of Altium, there was a maximum leftmost and downmost point it was not possible to view beyond. This is not the origin-point, however. What I'd do then, is before importing any components I'd move the origin point to somewhere up and to the right.
This will mean that any components imported with an offset like this can be reached, as they'll be placed beyond the origin-point, but not beyond the maximum view-point.