I'm getting the exact same thing... I've stopped playing (after 60 hours of the game... which I love) because I simply can't explore the caves... I can't even get the marble to make marble suits, because it's all in the caves. Even with full log armor and foot ball helmet the 9 worms tag team me for 1 hit kills.. can't get chester back.
My problem is I can't get back underground... to get marble... to make a marble suit. Chester is lost to me forever... I took 10 log suits, 10 honey salves, and multiple football helmets... prepped for a battle... and died in one hit from the worms. I just have a pile of stuff down there at the entrance of the caves... piled up from repeated attempts. And I'd swear there was more than 6... looked like 9 when they hit me.