Freeradius crashes after "Module rlm_sqlippool became unblocked for request"

Hello everyone! Could someone please help me about the warning message "Module rlm_sqlippool became unblocked for request" ? When this error happens, my freeradius server 'crashes' and then I need to start it again. I'm using version 2.2.2 with MySQL support. All radius tables are using InnoDB as engine of MySQL. Why this happens and why freeradius stop working? In the meantime, thanks for your attention and participation!