Traffic drop to zero when the simple queue is disabled

I have a pppoe server runing on CCR, in a given moment I would like to run a script that enables /simple queue on my external IP pool 2**.***.10.32/27
This part works fine, but when I want to disable this entry - I have a drop of packets to zero, even though the queue does not apply to the whole pool /24 but to the /27 part only. Why is this happening?
Device: CCR1036-8g-2s+ ros:6.43.11
I checked with queue=wireless-default/wireless-default and queue=default-small/default-small
same behavior.
q_drop.jpeg

To answer that, we would need to know how simple queue functions internally. To my knowledge that info is not available (publicly).

Wild guess: some clean-up which occupies all cpus?

I’d understand if the traffic dropped a little because the queued packets to the mask /27 would be dropped, but why it drops to zero? I did tests between CCR and 951 with bandwitch test and there was no such effect, but then the load was 100M and not 2G