In general you assume DAGs, i.e. non-cyclical causality. Cyclical relations must be resolved through distinct temporal steps, i.e. u_t0 causes v_t1 and v_t1 causes u_t2. When your measurement precision only captures simultaneous effects of both u on v and v on u you have a problem.
Comments
What of the double slit experiment, where observation changes the outcome? Do we call observation the cause of the outcome?
In general you assume DAGs, i.e. non-cyclical causality. Cyclical relations must be resolved through distinct temporal steps, i.e. u_t0 causes v_t1 and v_t1 causes u_t2. When your measurement precision only captures simultaneous effects of both u on v and v on u you have a problem.