[S15] The problem of unstable frame rate

My Computer Information: i7-8700k | DDR4 2666 | GTX1080 | Windows 11 21H2

I play apex at 1080p (all low quality in video setting) on a 2k monitor because if I play at 1440p (all low quality in video setting), the frame rate is not stable above 144fps during engagements.

I use "+max_fps 190" to unlock the game maximum frame rate, and then use MSI Afterburner to lock the frame rate at 144fps.

[Problem]:
Before season 15, the framerate was very stable when playing, but after the season 15 update, the framerate became unstable.

The unstable frame rate is reflected in irregular and unpredictable lag during playing, with the frame rate dropping to around 110fps instantly and then returning to 144fps in a short period of time.(This happens during non-engagement periods or engagement periods, or even in the training ground)

[What I have tried so far]:
I tried to upgrade the driver version from 512.15 to the latest 526.86, but it seems to be more serious than 512.15, and the lag is more frequent. So I returned the driver version to 512.15.

I tried unlocking the frame rate in MSI Afterburner, the game runs at 190fps and stays stable, engagements may drop to 170fps or so, but never below 144. the lag is still there after unlocking the frame rate.

After this problem appeared, I ran the DX11 benchmark in 3DMark, which showed that my computer could reach 140+ fps at full 1080p high quality (see attached image).