I am not sure why, but I am getting too many error logs. Sometimes happens that a function doesn't exist and then I got many WordPress database error for various blog ID's. I am not able to find any solution for this as it does for almost every blog in my network. E.g. in error log it writes "bp_activity function doesn't exist" and after this I got a lot of "WordPress database error MySQL server has gone away for query" and then another function doesn't exist, and again same message and so on. What can be the problem?