Water will not drain form tub

If your drain is not high enough the water will siphon out while filling. Check your owner's manual for correct height, usually about 39 inches from ground

If the water is entering through the overflow on the twist mech. then the gasket should be tightened and or adjusted. If possible feel around on the top of that fitting from the back side to rule out water leaking from other source, such as backsplash or faucet from escutcheons. It sounds like you have a pretty good idea of how to fix it. I hope this helps.

check sunroof drain holes are not blocked.

This is a condition known as syphoning. Your drain hose on the washer needs to go up before it connectes to the house drain. It needs to rise as high as the washing machine top then hook over the drain pipe. If the drain hose is pushed too far into the drain pipe this can also cause syphoning.

Here are some tips to help describe this better.

Is the drain hose extending more than 8" (20.3 cm) into the drainpipe?
The drain hose may be too far down inside the drainpipe (standpipe) or laundry tub. Drained water can siphon back into the washer if the drain hose extends too far. Make sure that the drain hose does not extend more than 8" (20.3 cm) into the drainpipe or laundry tub. Using the U-shape drain hose form (as described in the Installation Instructions), will provide the correct length of drain hose in the drainpipe or laundry tub.
Drain hose form

Is the drain hose taped onto the drainpipe? Is top of the drainpipe covered in tape?
Do not seal the drain hose into the drainpipe with tape. The drain hose should be loose, yet secure. There must be a gap between the drain hose and the drainpipe to allow air to flow. The air gap will break the suction. This will keep water from being continuously sucked out of the machine (siphoning) as it fills.
Is the drainpipe (standpipe) less than the minimum height of 39" (99 cm)?
Make sure that the top of the drain is at least 39" (99 cm) high (as measured from the floor.) If the drain is below 39" (99 cm), the water will start to flow out of the machine due to gravity. The flow of water can create suction (siphon) and the water will continue to drain out of the washer.

you have a blockage some where in the drain hose.most likely in the hose the comes form the bottom of the tub to the pump.you attach a wet dry shop vac to the end of the drain hose and remove the water this way while the vaccum is working look at the hose that comes form the tub to the pump and if it colapses then there is something restricting the water flow.also make sure to check in side the drain pump cover for any thing that is obstructing the pump

All the water does not drain. The front tub has ballance ring with water sealed in it to off set off ballance loads. The sump hose on the pumpwill also hold water. You can clean your pumps clean out trap to make sure the pump is working good. Also a drain hose higher than 6 ft off floor will cause pump not to drain all water. Front loaders all have a mold problem. no air gets in when your done washing because you close the door. If you dont use bleach and hot water washes it makes matters worse. Fabric softner is even worse.
You need to clean your washer with bleach in the front seal by hand some times.
Its the price you pay for saving water.

What you smell is algae forming in the pipes. If you have small black particles in the tub when running the jets, it is algae. Fill the tub with hot water, add 2 teaspoons of cascade dish soap and 1/2 cup bleach. run the tub for 15 minutes and drain. fill tub with cold water, run for 15 minutes and drain, tub is now ready to use. repeat as necessary.

I take it that you removed the drain trip linkage and stopper through the vent hole .
You must now run a small hand or small power snake the less than eight feet to open the drain.
You can also plug up the vent,tightly and  try a flat plunger on the tub drain .  

This usually is caused by a detiorated O ring that compresses to make a watertight seal at the transistion points from them drain shoe and overflow tube to the trap adapter. However it may be the trap adapter as well. Either way the best solution is to access the tub waste from the wall behind the tub drain and replace the necessary parts. Your issue is showing up because the gallons per minute/hour rate that the tub drains is far greater than the tub valve is allowed to fill the tub. This causes a greater volume of water to fill the tub waste and as such the backpessure is greater as the entire volume of water in the trap weir must be evacuated as opposed to when the tub is not plugged and the valve is ran requiring the trap weir to evacuate gradually. Some tub wates are made of metal and may have developed holes in them but they generally form along the pathway the water uses to drain. Unfortunately the only real solution is gain access to the tub wate and replace the defective part. Thanks for using Fix Ya.

Check to see if there is an open valve where the water exits the tub. If there is a valve, shut it and your problem should be solved. good luck