BroccoliRob said:
You might just need to find a different manufacturer. MAybe a different company's 4-way switch would have a different design and not give you this problem
Yep, you're right. I spoke to Warmoth today on the phone. He told me that they have never had this issue with their 3-way blade switch, but he's never heard from anyone who has run a 4-way.
That leaves me with the conclusion that it is definitely switch related. I'm not even sure if any 4-way switch will work. I may just have to go with a 3-way switch, which honestly wouldn't be the end of the world.