@Sit75
Referring to your post (> http://forum.mikrotik.com/t/v7-14-3-stable-is-released/174007/482 ), did you assign a fq_codel_queue_type with 32MB buffer for each member of the queue tree?If so, then the queue buffer clearly exceeds the RAM of your hAP ac² and and could lead to this behavior.
My configuration is below. I simply mark the uplink traffic according to DSCP high 3 bits (with preference of ACK packets). Outbound traffic is divided into standard 8 queues under one outbound queue tree. Downstream traffic is handled by a single untagged queue. I didn’t change any default buffer sizes or anything else. IP and IPv6 Mangles are identical copies. This configuration is the best from a bufferbloat perspective with absolutely minimal latency (9ms) and minimal latency variation (+3-4ms) under full load. That’s the reason.
/queue type
add fq-codel-limit=1024 fq-codel-quantum=300 kind=fq-codel name=fq-codel-ethernet-upload
add fq-codel-limit=1024 fq-codel-quantum=600 kind=fq-codel name=fq-codel-ethernet-download
/queue tree
add bucket-size=0.01 comment="Upload Link" max-limit=25M name="DSCP->Priority - upload" parent=pppoe-out1 priority=1 queue=fq-codel-ethernet-upload
add comment="DSCP 01-07 (Priority 8 - Lowest)" name="8. Routine - upload" packet-mark=priority_8 parent="DSCP->Priority - upload" queue=fq-codel-ethernet-upload
add comment="DSCP 08-15 (Priority 7)" name="7. Priority - upload" packet-mark=priority_7 parent="DSCP->Priority - upload" priority=7 queue=fq-codel-ethernet-upload
add comment="DSCP 16-23 (Priority 6)" name="6. Immedate - upload" packet-mark=priority_6 parent="DSCP->Priority - upload" priority=6 queue=fq-codel-ethernet-upload
add comment="DSCP 24-31 (Priority 5)" name="5. Flash - upload" packet-mark=priority_5 parent="DSCP->Priority - upload" priority=5 queue=fq-codel-ethernet-upload
add comment="DSCP 32-39 (Priority 4)" name="4. Flash Override - upload" packet-mark=priority_4 parent="DSCP->Priority - upload" priority=4 queue=fq-codel-ethernet-upload
add comment="DSCP 40-47 (Priority 3)" name="3. Critical - upload" packet-mark=priority_3 parent="DSCP->Priority - upload" priority=3 queue=fq-codel-ethernet-upload
add comment="DSCP 48-55 (Priority 2)" name="2. Internetwork Control - upload" packet-mark=priority_2 parent="DSCP->Priority - upload" priority=2 queue=fq-codel-ethernet-upload
add comment="DSCP 56-63 (Priority 1 - Highest)" name="1. Network Control - upload" packet-mark=priority_1 parent="DSCP->Priority - upload" priority=1 queue=fq-codel-ethernet-upload
add comment="Download Link" max-limit=120M name="Download Link" packet-mark=no-mark parent=bridge queue=fq-codel-ethernet-download
/ip firewall mangle
add action=change-dscp chain=postrouting comment="ACK -> DSCP 34" new-dscp=34 packet-size=0-123 passthrough=yes protocol=tcp tcp-flags=ack
add action=set-priority chain=postrouting comment="Setting priority from DSCP high 3 bits" new-priority=from-dscp-high-3-bits passthrough=yes
add action=mark-packet chain=postrouting comment="DSCP 56-63 Priority 1" new-packet-mark=priority_1 out-interface-list=WAN passthrough=no priority=7
add action=mark-packet chain=postrouting comment="DSCP 48-55 Priority 2" new-packet-mark=priority_2 out-interface-list=WAN passthrough=no priority=6
add action=mark-packet chain=postrouting comment="DSCP 40-47 Priority 3" new-packet-mark=priority_3 out-interface-list=WAN passthrough=no priority=5
add action=mark-packet chain=postrouting comment="DSCP 32-39 Priority 4" new-packet-mark=priority_4 out-interface-list=WAN passthrough=no priority=4
add action=mark-packet chain=postrouting comment="DSCP 24-31 Priority 5" new-packet-mark=priority_5 out-interface-list=WAN passthrough=no priority=3
add action=mark-packet chain=postrouting comment="DSCP 16-23 Priority 6" new-packet-mark=priority_6 out-interface-list=WAN passthrough=no priority=2
add action=mark-packet chain=postrouting comment="DSCP 08-15 Priority 7" new-packet-mark=priority_7 out-interface-list=WAN passthrough=no priority=1
add action=mark-packet chain=postrouting comment="DSCP 00 -> Priority 7" dscp=0 new-packet-mark=priority_7 out-interface-list=WAN passthrough=no
add action=mark-packet chain=postrouting comment="DSCP 01-07 Priority 8" new-packet-mark=priority_8 out-interface-list=WAN passthrough=no priority=0
/ipv6 firewall mangle
add action=change-dscp chain=postrouting comment="ACK -> DSCP 34" new-dscp=34 packet-size=0-123 passthrough=yes protocol=tcp tcp-flags=ack
add action=set-priority chain=postrouting comment="Setting priority from DSCP high 3 bits" new-priority=from-dscp-high-3-bits passthrough=yes
add action=mark-packet chain=postrouting comment="DSCP 56-63 Priority 1" new-packet-mark=priority_1 out-interface-list=WAN passthrough=no priority=7
add action=mark-packet chain=postrouting comment="DSCP 48-55 Priority 2" new-packet-mark=priority_2 out-interface-list=WAN passthrough=no priority=6
add action=mark-packet chain=postrouting comment="DSCP 40-47 Priority 3" new-packet-mark=priority_3 out-interface-list=WAN passthrough=no priority=5
add action=mark-packet chain=postrouting comment="DSCP 32-39 Priority 4" new-packet-mark=priority_4 out-interface-list=WAN passthrough=no priority=4
add action=mark-packet chain=postrouting comment="DSCP 24-31 Priority 5" new-packet-mark=priority_5 out-interface-list=WAN passthrough=no priority=3
add action=mark-packet chain=postrouting comment="DSCP 16-23 Priority 6" new-packet-mark=priority_6 out-interface-list=WAN passthrough=no priority=2
add action=mark-packet chain=postrouting comment="DSCP 08-15 Priority 7" new-packet-mark=priority_7 out-interface-list=WAN passthrough=no priority=1
add action=mark-packet chain=postrouting comment="DSCP 00 -> Priority 7" dscp=0 new-packet-mark=priority_7 out-interface-list=WAN passthrough=no
add action=mark-packet chain=postrouting comment="DSCP 01-07 Priority 8" new-packet-mark=priority_8 out-interface-list=WAN passthrough=no priority=0