Welcome to the Q&A Forum

I have a regional careers website on a small seo retainer contract. I manage the google webmaster account and use moz tools to help keep pages finely tuned. The site has been experiencing a phenomena now for about 6 months whereby the SERPS (we work with around 10 keyphrases) are placed in top 5 positions and generate healthy google traffic and will then suddenly vanish. The cycle is roughly 1 - 2 weeks top page, followed by 2 - 3 weeks outside the top 5 pages of google results. I contacted Google via webmaster central to ask for help and they simply confirmed that there were no penalties being applied and it was normal algorithm updates. I manage the seo for 20+ sites and have not seen this phenomenon elsewhere, not since the days of 'google dance' years ago. Has anyone else had this experience ? The SERPS always come back after a couple of weeks but then vanish again after a week or so this cycle has been ongoing for 6 months now and we have eliminated all symptoms we can think of. Your feedback would be much appreciated in this matter.