zeek cluster stop worker

Hi, I set up a zeek cluster which looks like this:
[logger-1]
type=logger
host=localhost
[manager]
type=manager
host=localhost
[proxy-1]
type=proxy
host=localhost
[worker-1]
type=worker
host=localhost
interface=enp59s0f0
lb_method=pf_ring
lb_procs=5
pin_cpus=2,3,4,5,6

Zeek is started normally capturing correct packets. But when I stop zeek using zeekctl stop, it takes a long time and shows
worker-1-1 did not terminate ... killing ...
worker-1-2 did not terminate ... killing ...
Why is this happening? How can I solve it?