RB11000AHX4 FASTTRACK icmp and udp unstable

Hello , my router model is RB11000AHX4. After enabling the FASTTRACK function, my ping in the game is unstable and fluctuates greatly.
I tested the network and found that ping 8.8.8.8 has unstable latency and frequent fluctuations. Under normal circumstances, it is 4ms, but when there is a fluctuation, it will jump to 20ms or 50ms.
When the FASTTRACK function is turned off and the router is restarted, it is normal without any ping fluctuations.

The following rules have been activated in the filter rule of the router:

/ip firewall filter add chain=forward action=fasttrack-connection connection-state=established,related
/ip firewall filter add chain=forward action=accept connection-state=established,related

The current firmware version is v7.15.1, and replacing v7.11.2 and v7.5 is also the same issue.
Please help me solve this problem, thanks!!!
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