I'm afraid I won't be of too much use here, but it did occur to me to ask whether you really mean 50MB (as in 50 megabytes per second, or 400 megabits per second)? I'm assuming that's the case, because 50 megabits per second certainly shouldn't be stressing anything. Additionally, is the connection symmetric (50 upstream too)?
Also I don't know whether this is really an option, but if possible I might suggest backing up your configuration and performing a fresh installation. Then you can see whether the problem exists even when you're starting from zero with no packages installed.