In my case, people from Litecoinpool have found that my miners firmware requests unusually high share difficulty. I use Titan miners with Gen Tarkin mod. Earlier this request caused no problems, because the share difficulty maximum at the pool was much lower. A few days ago the maximum was increased to allow better compatibility with large mining operations. In effect my miners are getting what they ask: very high share difficulty, so they submit the shares so infrequently that the pool is unable to estimate the short-term speed of my miners. The solution/workaround is in the works.
Thank you.