Sorry Chaffordred - it's a 405 I was meant to hold off until Xmas for, but I bought a few weeks ago for this race, so I not just about press start & stop and that's it!! I've had similar problems with it and, typically, Sunday was one of few times it's worked to perfection!
Prior to buying though, I did check out an RW gear forum for it and some guy was on there that seemed to know everything. Asking him might be worth a try! Good luck - if it was me, I'd be doing what I could to replace the 6,000 calories I'd lost!!!!!