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Phil is always right on.

As he says, placing the trailer as deep as practical will help. Karavan is a bunk trailer so friction is a factor. The deeper the trailer, the less friction. Karavan is also a good trailer, and they have great service. And you most likely have the swing tongue.
Many of these discussions take into account the ramp you primarily use. Some discussions forget that the angle of the ramp is very important. Therefore, you may want to consider which ramp will be your most frequent and adapt to that one.

There are also many discussions of products to smooth the bunks.
I would begin with liquid rollers spray. Then there are a bunch of plastic "slicks" that can be added.
With our lake down, We are launching from the shore. The slope is often too gradual, so I added plastic bunk caps. They help. The style of these caps and is a whole new discussion and that can most likely be found in search.
As Phil mentioned, technique is truly the primary factor.

One more thing, "difficult to load" is subjective from one to the next person; so we do not really know how much strain was on your winch. When pulling with lines cables and even straps, beware of the kick back if they break. Even a short length will snap back if it breaks. It is just a good habit to stay to the side and out of line of anything under stress.

Good Luck