it's a hardware problem, mine stop freezing with one of the patchs released  this year, sorry but is only your wiiu, call nintedo.

Let me explain further: Do you have an external HDD? Because that is where the issue lies. Without using the external my Wii U never freezes. It froze less often when I didn't have over 150GB of games on it as well. It definitely has something to do with the way it's reading the HDD. And with every other patch Nintendo manges to fix the problem and then make it happen again with the following patch. 

I have bought 2 new HDD's and the one I currently have connected is only 3 weeks old, I bought it when I got my Wii U back from Nintendo. If you have an external drive, I found a way to prove that it's pretty much the way the system is readint the HDD. Put in a game, start it then pause it, let it sit idle for about 20 minutes then hit the home button and attempt to close software. 8 out of 10 times it will freeze.

Edit: I havee spent a lot of time and money on my Wii U, 3 different HDD's and have sent it to Nintendo 2x. If Ninty hasn't figured out how to solve the issue 2 years in, I doubt they ever will. Either way, I am through spending money to fix a problem that will never be fixed.

Edit 2: It is downloading Bayo 2 now.

Except ninty will just make me pay for them to check it out and then tell me there was nothing wrong with it like they did last time. It's the OS. I don't know why they can't get their shit together. I have called nintendo numerous times and at this point I am just about done with this console. 

I will attempt on more time, if the console freezes while downloading bayo 2 I will stick it in a box and never touch it again. It will go into the collection room.