Description
For objects that are not "naturally" numbered by LaTeX, we "label" them with a \hypertarget. If such an item is implemented as a tcolorbox, then it is usually with an option such as:
phantom={\hypertarget{#4}{}}A cross-reference is then implemented as a
hyperlink{}{}Problem: following the link lands on the second line of the target.
\phantomsection does not seem to help. Techniques suggested here were not successful:
https://tex.stackexchange.com/questions/17057/hypertarget-seems-to-aim-a-line-too-low
A single experiment (with the sample article exercise "42a") suggests a tcolorbox phantomlabel=<label> and a cross-reference as hyperref[<label>]{<hard-coded-number-etc>} will work better.
This will require identifying which objects are tcolorbox (or will be), which have an accurate number from the LaTeX re/label mechanism, and which need hard-coded numbers. Ideally, all items requiring hard-coded numbers will be implemented as tcolorbox (or are specialized divisions integrated into the titlesec mechanism).