Instead of "_usr_bin_restricted-manager.1000.crash" check if there is a _usr_lib_firefox_firefox_bin.1000.crash file in /var/crash. It should be several Mb of size as it contains the firefox crash coredump file.
Instead of "_usr_bin_ restricted- manager. 1000.crash" check if there is a _usr_lib_ firefox_ firefox_ bin.1000. crash file in /var/crash. It should be several Mb of size as it contains the firefox crash coredump file.