Prius 2017 3 - Curt 56353 trailer light harness issue

Bought this harness twice and had professionally installed each time over the past four months for a small trailer using LED lights. Worked at first, but quickly failed so that right side lights were not working (except sometimes a short section of the led strip had dimly lit red lights. Took into Toyota today and could not resolve the issue. Car lights work fine alone, as do trailer lights. Suspected that voltage overload when using several light functions is frying the little black box. A temporary workaround allows me to at least use turn signals or warning flashers, but no brake/running lights. Reviews seem to show this works (as Curt tech support said they never had any issues and the problem probably lies in the car and/or trailer since it happened twice). A couple of users have reported problems reported on the website, but reviews tend positive. Any insights?