Rewards are 100% based on the price of scrypt coins that can be asic-mined (LTC mainly), and whatever Scrypt.cc decides to take out of those rewards, like electricity. If the return drops on those coins, the rewards drop (usually about a 24-48 hour delay before it seems to impact rewards though, which makes sense if they are doing profit switching smartly, rather than just dumping mined coins as quickly as they can).

Your rewards have nothing to do with the trade engine & site, which is solely peer-to-peer trading of KHS, chat, and account reporting. When that system is getting DDOS, or lags for any number of other reasons, you will get delays in deposits, withdrawals and trades... things usually self-correct and catch up, and in the rare instance they don't, 1 simple ticket will usually work. Those problems never have an impact on mining though, since those server addresses are kept confidential. For a reason. I don't think I have ever seen a mining slowdown since Feb 2014 (although there  must have been one or two)