So, I've been having an odd issue and thought I'd post in the off chance that anyone has ever heard of this.
If I play with a Wii Remote (or Nunchuck, CC, etc. attached to one), it will randomly cut out during a match every few seconds or even multiple times in a second. By "cut out", I mean it will act as if I let go of a button and then started pressing it again. The best way I've found to test is to start a match and then hold down to make the character crouch. If I'm using a Wiimote, the character will occasionally stand up and then immediately crouch again. This is very troublesome when trying to play because, for example, it will make the character do a double-jump when I didn't intend it, and so on.
This happens on both my Wii U and my Wii, with all of my four Wii Remotes (two of which are Pluses), though seemingly only with Brawl (and Project M), and no other game on either console. Wavebirds and other GameCube controllers don't exhibit the problem during the same matches when the Wiimotes do.
I've searched around online and the few instances I've found were solved by people turning off their wireless speaker systems. I have no such system. I'd blame it on interference from my new apartment building, but the same thing happens in my parents' rural house hundreds of miles away as well as my friends' apartment a couple dozen miles from there. I doubt they all have the same interference going on. And there's the fact that it only affects this one game...
Has anyone ever heard of this? So strange...