Stock Phase 90 ground problem?

[bassmeister]

Hi,

My Phase 90 stopped working the other day. The LED lights on and off with the foot switch, but when it's on, the sound comes through but I get no phasing effect. When I touch the foot switch gently with my bare hands, everything works OK. It also works fine when I touch the nuts holding the in and out jacks. I opened the box, but I just had time to take a quick glance and the solder side looked OK, i.e. no obvious bad solder joints.

Any ideas on what's causing this?