This bugfix was added to the wiki of Zombiemodding but the link no longer works.
What happends? After you got hit by the Wunderwaffle multiple times your health will be set to 1 instead of 100 and does no longer regenerate.
This is the backfire of using the weapon like the Raygun.

How to fix it?

1. copy _zombiemode_tesla from CodWaw/raw/maps to your mod. If you already have one it's fine.

2. Openup the file and look for this:

if ( self == attacker )
{
    damage = int( self.maxhealth * .25 );
    if ( damage < 25 )
    {
        damage = 25;
    }

    if ( self.health - damage < 1 )
    {
        self.health = 1;
    }
    else
    {
        self.health -= damage;
    }
}

Change it to this or remove it:

/*
if ( self == attacker )
{
    damage = int( self.maxhealth * .25 );
    if ( damage < 25 )
    {
        damage = 25;
    }

    if ( self.health - damage < 1 )
    {
        self.health = 1;
    }
    else
    {
        self.health -= damage;
    }
}
*/

3. Build your mod and you're done!
Offical link: http://wiki.zombiemodding.com/index.php?title=Jugg_and_wonder_Fix