We have the stackables, but they are not stacked. They are each on separate shelves that I reinforced for better strength and stability. We've not had any issues AFTER we learned how to use them. They do have some quirks, become unbalanced easily, and occasionally throw an error code. Most of the time, it's because of an unbalance situation. Easy to solve.
We did have the dryer repaired by a mobile tech about a half year ago. I weighed the issue of just getting a new dryer or paying the price for the repair. The repair was the cheaper of the 2 and since we have not had any issues in the past, that was our decision.
It turned out to be "user error" actually. The dryer vent MUST be cleaned out ever now and then. Not just the hose that runs from the dryer to the wall, the workings inside the dryer itself. Ours was clogged with lint, which caused an overheating, which caused our problem. Now, about once a month I use the vacuum sweeper hose and suck as much out as I can from the lint trap area on the dryer, hopefully, will pull some of the lint out farther down where it can't be reached.
Had I known then, I might have spared myself a repair! Well, it did take 5 years before it became clogged up!