This isn't Hyundai's most reliable transmission, but it isn't their worst,
either.  To put things in perspective, I wouldn't expect to get more than
100k miles out of the trans without needing significant overhaul work or
replacement.  

There have been some issues with the pulse generators (input and output
speed sensors) and with the connector where they attach to the harness.
If that's the case, you will typically get either trouble code P0717 or
P0722.

There are actually several very informative technical service bulletins on
your vehicle which describe symptoms, trouble codes, and solutions.  I'd
recommend going to www.hmaservice.com and browsing through the
transmission tsb's for your vehicle.  

At this point, without knowing what exactly was found in each instance,
it's difficult to determine whether you've simply had a series of
unrelated problems or the dealer hasn't been fixing it properly.  I'd lean
to the side that it was fixed properly at least on the last visit if it had
been operating normally for five months.