Like all the 1970s-1980s "post-oil-crisis" super-efficient aircraft, it had a lot of problems.

The Beechcraft Starship is the best documented example, but this came from the same movement. It used two PT6B turboshafts both driving the same propellor, so it was meant to offer the safety of a twin engine but the handling of a single.

The body was semi-laminar flow, in an era before CFD, so all wind-tunnel models where laminar flow is notoriously hard to measure. Smoke streams don't show it well and tags interfere with it. This led to the V-tail having a lot more drag than was predicted. Said tail also didn't have blended pitch and yaw, instead relying on a tiny little rudder attached to the tiny little inverted vertical stabiliser to provide yaw and, as airflow over the two Vs interacted, pitch control was very powerful in a nose-down command, but weak with a nose-up control.

The "twin engine reliability" was also looked at with, as my son would say "bombastic side-eye" by the FAA, which correctly noted that an absolutely unproven single gearbox was all that stood between both engines and no power.

To achieve semi-laminar flow, a composite fuselage was manufactured in a day where composites were very new and unproven. People using them on bicycles were complaining about their tendency to fray and crack. This was not a bicycle. Pressure cycle testing showed the fuselage to be an in-flight structural failure waiting for the best time to happen.

The Lear Fan was a lot of new, unproven, untested, first generation technologies all in the same aircraft. Had more been made, it would have absolutely proven to be one of the least safe aircraft ever built.