I think the likelihood of a major malfunction is fairly low but I'm not familiar with that product so its a "measured risk" your taking. In one of my past jobs I would meet with UL on occasion, typically after workplace accidents. It was not unusual for a product to meet a UL standard (Make sure the product standard its certified to is actually relevant by the way) in testing then become "lax" later in manufacturing and some production runs not meet the spec but still get sent out anyway, more common then people (or I at the time) want(ed) to believe. Some products will also readily meet the specs for the UL listing but the manufacturer doesn't want to pay UL on its "per unit" cost to put the logo on the box/product so it doesn't have it. For what its worth, You'll not find a circuit breaker in a mines that is 1,000V rated (Despite the circuit being 1000VLL) that has a UL listing (save for a few when Eaton made a run and then later stopped). This is despite the fact that federal law requires it MSHA can't enforce a standard that no one is building to so its not enforced. Just FYI.