This question lacks specifics. So, my answer will have to be somewhat broad.
Whenever there is a problem of response rate or missing data, there can be many problems, as you can imagine. Therefore, it is important to rectify these problems as soon as possible or to mitigate these problems before they create larger ones. In light of this, let me offer a few solutions.
First, if someone is responsible for entering the response rate, then you should talk to that person. If the response rate is not due to a human factor, then you should put some thought into making this faster. The use of technology might help. You might want to consult with people in technology to optimize speeds.
Second, missing data is problematic, because this can skew everything. In light of this, you will need to figure out why there is missing data and determine whether this missing data is important enough to give you wrong results. Also you might want to create a few conclusions based on the missing data. Put in an upper limit and an lower limit and see how much changes in terms of your conclusions. Use the worst possible scenario to go forward, as this will be the safest route.
The key will be to rectify these problems the second time around.