Unlike space-time theory, where there is substantial agreement about how to understand the best physics we have (General Relativity), quantum theory … - Tim Maudlin

Many... would agree that Relativity prohibits something from going faster than light but disagree over just what something is.

[T]he most general question we can ask about matter is what sort of thing it is. ...[W]e might hold that matter is made of point-like particles, or of fields, or of one-dimensional strings, or of some combination of these, or of something else altogether. Given any of these ...there are further, more specific questions ...We will be concerned with the most general questions, rather than the more specific ones.

The central problem facing attempts to understand a quantum theory is how it manages to model empirical phenomena in a principled way. This is often referred to as "the measurement problem"...