My husband's favorite saying is "think like a drip".  Water will travel in a logical manner, taking the route of least resistance.

It your trailer parked nose-down by chance?  Water could be getting in back in the horse compartment and finding its way all the way to the front of the trailer.

With an equipped LQ trailer, there are many points of entry for water. Because water travels horizontally as well as vertically, it can sometimes be difficult to discover its source.

You have many potential entries into your living space. Vents and covers, A/C unit, antennas, lights, awning attachment points, windows, seams etc. A detailed search while carefully inspecting each caulking at every joint, may result in the discovery of improperly applied or cracked sealant, tree limb damage or even missing components.

Make sure the drain holes are open on the bottom channels of your sliding windows. If they are plugged, water can back up and weep inside. Often times the exterior lights are not sealed well on their backside when they were first installed. Smearing sealant around their edges, isn't as good as unscrewing the base from the trailer and applying new sealant around the wire hole.

Unless you find an obvious point of entry, you will have to use a process of elimination and much perseverance.

BOL  Gard

My Featherlite leaks both in the gooseneck and box. It's not a LQ but it's insulated and paneled and the paneling is stained from the water.

Our trailer isn't under warantee, it was acutally made before Featherlite extended their's to 8 years. Perhaps yours is covered and it can be fixed at no cost to you?