Just returned from our first vacation with our C241RLK

Glad you had a great outing and all with no major problems.

What is the voltage at the battery when not connected to anything? What is it when connected to shore power?

How are you trying to fill the water tank? Gravity fill with a hose squirting in? Pressure fill thru the city water inlet?

Do you have 12 volt power to the refrigerator? Does the stove burners light?

Regarding your electrical problems - we have a different model but recently had to replace the auto-reset circuit breaker. It is located about about 1 foot from the battery on the +12V side. Our symptoms were similar to what your are describing.

For several years KZ did have pressure fill systems, where you opened a valve to allow water to flow to the fresh water tank. I doubt that the OP has this system, but unless he gets back to us we can't help.

As a side note, I had that faulty system, that spilled water, and now have it highly modified to allow gravity fill, pressure fill, external tank usage and tank fill from an external container. I didn't need to add expensive parts and the original pump does the work as needed.

Glad you enjoyed your new trailer.  We also bought a new C241RLK and spent almost 3 weeks in Wyoming and Montana.  We enjoyed the trailer immensely and no problems except first day had an A/C wire come loose but was diagnosed and fixed easily by a local dealer in west Nebraska.  We really like the rear living arrangement.  One thing I am changing is the access to the slideout.  I like to check the top of the slideout before retracting to make sure there is no debris to damage the seals.  However, the ladder is a little narrow for my use on a regular basis.  I therefore bought a telescoping ladder that has a much higher capacity and telescopes down to a small size.  I can leave it extended to 8' and bungee to the tongue or rear platform for easy access.  I can now inspect the top of the slideout much quicker and with more confidence of not falling.  We are looking forward to some fall trips.

It was a nice campground. It was at Shoshone National Forest on the east side of Yellowstone. I'm thinking about one of those slider toppers also; I read good things about them.

I'm curious; the 241 RKL indicates it is 24' front to back of the living area without the tongue.  Have you measured yours?  I measured almost 26'; the salesman was even surprised.  Also, have you done actual tongue weight measurements?  I measured 600# on a certified scale.  The weight includes two tanks of full propane, no water or wastewater.  Specs call 560# which is really close since they weight without propane.
My trailer with propane, spare tire, rear luggage rack, no water or wastewater weighs 6,120#.  The trailer sticker shows 5.600# unloaded with a 580# tongue weight.  
Tongue weights are very close to my scale but empty weight is 520# difference.  

I could reduce some of the weight by excluding my normal travel items such as sewer hoses, level blocks, water hoses, etc. However, if wouldn't make a huge difference and they are required items.
If you get weighed, I would really be interested in your results. I measured the cabin at the longest length, just above the outside access door.

When I was looking for a new trailer (lots of brands and dealers) I was amazed at the things they would tell me which I knew to be untrue. I sometimes wonder if they ever read their own brochures.
I am a structural engineer and pay attention to all those little details (My wife says to the extreme sometimes) but it sure helps. When I was looking, the weight of the trailer, hitch weight and combined weight of my tow vehicle was very important. Between the trailer and tow vehicle (set up as if traveling but without personal items or water); I am at the practical gross weight limit.
However, I am quite a bit under the allowable towing weight for my Tahoe and substantially under the tongue weight.

Speaking of tongue weights. Since my vehicle is fairly short, even with a 800# distribution hitch, I would still get a little bounce. My hitch allowed me to buy stiffer torsion bars so I bought the next size up, 1000#. Last night I had a chance to hook up and test drive; it helped quite a bit and I can even make it stiffer if needed.

Your turbo diesel truck sounds like you can pull about anything your heart dreams! We pulled through the mountains this summer and the Tahoe was feeling the load but I never felt it was struggling and I could keep a good speed up. There were a few rare exceptions when it was very, very windy but overall had no problems.