Epinephrine error

Recently I witnessed a medication error with epinephrine, the patient was a 26 year old female, written for 0.5mg of epinephrine sq due to a allergic reaction to a medication, PT had hives/facial swelling. The patient was given 0.5mg of epinephrine 1:10,000 IV push. The patient for a few moments had sinus tachycardia, shortness of breath, chest pain, decreased vision & the feeling as if they were going to pass out. After a minute or so vitals were back to baseline & the patient only had complaints of a headache. Patient was admitted for observation, troponins/ekg were normal, echocardiogram was normal, also a Mri of the head was done as the patient had continued headache which was negative for any findings. My question is do epinephrine errors happen often? Also, I'm curious how this patient received such a high dose of epi but had no harm done, seems rare.....