Since V6.6.1, to be exact since commit 291c7a0 "Make signal handling safe using pselect.", the child process started by procServ cannot be terminated with SIGTERM any longer. In particular --killsig 15 does not work.
The reason is probably that the child inherits the signal mask which blocks SIGTERM (and SIGPIPE and SIGHUP).
Signal mask should be reset to "normal" for the child.