The quick cycle used to be around 29 minutes; it's now 56 minutes. Why did this happen?

Check the heating element. A quick functional test is to start a cycle that uses the heating element, cancel it after a couple of minutes into that cycle, then (carefully) put your hand near it to see if it is warmer than the surrounding parts. If not, start there.

If you are familiar with the use of a multimeter, and you can get at the underside of the dishwasher, you would disconnect power to the dishwasher, find the heater terminals underneath, then measure the resistance. It should be a low value, not more than a hundred ohms or so (this type of heater probably has a resistance around 10-30 ohms). Look for oxidation on the terminals or connectors on the wires. If there is corrosion, (especially signs of water leaking onto the terminals), clean that up and fix any leaks. If the heater reads open, replace it.

Code 12 is a flame failure.
First step in diagnosing the root of the issue is to check for any separation, obstruction, or failure in the vent system.
Second step is to use the isolator kit under the heater to flush the heat exchanger with vinegar or rectorseal calci-free.
These two things are a great starting point to working on any tankless water heater. Flame failure can be as simple as the heat exchanger being clogged not allowing the sensors to work properly or the exhaust being mixed with the air intake. If the problem persists I would suggest having a Rinnai Certified Tech look at the heater.

Feel water temperature when dishwasher stops. it is likely the heater is faulty. Does this happen in the cold water wash cycles?

Try unpluging the dryer for 5 minutes and then plug back in. See if that did it. Electrical outages and power surges raise issues with so many appliances these days. Hope that does it for you.

the purpose of that tube so it anywater that comes out of it goes through it and directs the water down the back and away from the motor. Now the bigger issue is why is water coming through that tube.What i suspect the reason of that is that the transmission is defective and the break is that internal to the transmission is slipping so the inner tub turns during the wash cycle force water up the side of the tub into that tube.during the agitate cycle the tub is not suppose to move at all and stay locked into place,but instead its moving where the water is forced up by centrifical force too and out the top of the tub cover,if it leaks with only a small water load it will leak worse with a large water load. if this is what is happening and the tub is rotating on agaitate cycle teh fix for that is to replace transmission which in most cases cost as much as replacing the washer would be

Check your heater by-pass valve and be sure it is almost closed. If not that then it will be your internal by-pass. These will force water through heater and keep it from overheating the water inside it and shuting it down. Also check to be sure the baskets are clean and the filter is clean.

d sounds as if your having a timer issue here. not recognizing the end of cycle and entering a new one ( bad timer).. as far as time of unlocking this is normal, theres a wax motor holding the door shut for i believe 3 min's.. and the water sloshing sounds is also normal they use a "water filled" balance ring around the perimeter of tub to help with the overall balance of machine

remove the lower acess panel and there is a tech sheet / troubleshooting guide taped to te back side of it,, in there is detailed explaination of all your issues you may encounter with your machine.
I usually set to a test/diag mode and check to make sure your heater is working, after that if heater check ok youd want to listen for proper water amount being pump around interior of d/w(usually you can hear not really pumping with much force).
try pushing the sani-rinse. heated dry, sani-rinse, heated dry.. all lights should lite, indicating your in hte diag mode, it will then cycle through the tests afeter about 45 secs or so the motor will engage immedialty open the door assy and feel the heater coil for heat,if cold cancel test with the cancel button and try again.( i like to confirm the heater cycle twice),if you coil is still cold refer to the heat cycle test strip for repair.
aferer exiting hte test the clean light willnolonger be blinking regardles of repairing issue or not. perhaps it was a fluke happening youll be alble to run you unit, should it happen again immedialty youllnknow you a problem yoll need to adress

There is a service manual behind the control panel it will show you how to test the door locks. If might have a bad lock solenoid.

Aestaie, On the quick wash cycle the machine goes through a heated rinse at 160 degrees. I think what's happening here is that the board checks the thermistor and is finding that the water is not hot enough and say's, hey, I need more time to heat this water and resets itself. The element in the dishwasher will only heat the water 1 degree every 3 to 5 minutes. So after the initial wash, there is a 2 minute drain, it fills again and there is the heated rinse. If the water is 120 and the final rinse needs to be 160, we have some heating to do here. Therefore the reset. Sounds like the dishwasher is working OK, Catriver..post back