Treacherous technician syndrome:

Treacherous technician syndrome refers to a limb lead reversal that usually occurs due to the technical error of reversing the right and left arm electrodes. Treacherous technician syndrome has become more common as non-experienced personnel replace electrocardiogram technicians. Treacherous technician syndrome is the most common cause of situs inversus (or dextrocardia) false-positives.
Limb-lead reversals (LLRs) remain clinically problematic.