I removed the crisper drawers and bottom shelf on mine. It allows me to fit 2 kegs with stuff in between them. Yeast jars also fit perfectly on the back ridge. I also do the occasional carb burst after a few beers like KevinM.
What percent of the total water do you mash with? I've just been mashing with all of it, but it doesn't seem to tough to mash with a little less and use that to sparge instead.
I have the same problem with one of my liquid posts. It seems like it's screwing into the dip tube, as it gets stuck before it even makes it to the threading it's supposed to screw into.