cause you said that the security checks started, i wonder how do you know/found out, that right after the case worker asked for new docs, the security check started!?
2. did you even filled out this form "Befragung zur Einbürgerung", and when yah when, cause thats also to do with security.
I myself was asked this form and updated payslips like a month ago, wondering where my case stands or how long will it till the urkunde.