I posted about this problem on old forum, and didn't get any valid explanation or way to fix this issue, but over time it just went away. In November 2020 I decided to start grinding again, and noticed some weird FPS stutters that happened every minute. Almost exactly every 60sec. So I made recording of that problem:

I never got any reply from Kakao or PA support about this problem, but for some reason after some time this problem went away. But since 17th February I'm now getting same problems again, so made 2 new videos. One before transfer from Kakao to PA, and one today, after transfer. Problem is back once again, and I have no idea what's causing those FPS problems. I didn't change anything with my PC, no new software, drivers or anything. There are no scheduled tasks on my PC that would run every minute and cause that stutter.

I closed all apps except BDO, and problem is still here. Tried to follow a bunch of guides for improving gaming performance on Windows 10, but still the same.

Hopefully someone from technical support can try and figure out what's the problem here.

New videos are still uploading and converting to HD quality on YouTube, so it will take some time before those will be shown here correctly. In the meantime you can check video above. I also added timestamps of those stutters for each video in YouTube description.

My PC specs:

Windows 10 PRO 20H2 with latest patches

i7 9700KF at 4,7GHz (No AVX offset)

RTX 3070

32GB DDR4 3200MHz CL16 RAM

Z370 EVGA motherboard

Samsung SSD 860 PRO 512GB (drive of BDO and Windows install)

500/100 dedicated connection with MikroTik router rules, so one user doesn't overload entire network.

Yeah this sux, big time, i don't think they will fix this! 

I'm sorry this is happening to you. I don't wanna spam at all but this is the only way I can offer you some help. I have a -> Reddit Guide <- you can definitely try. It has served many people succesfully.

Unfortunately your guide will not fix the stutter, but thank you!

The same thing to me in SEA server, I had the same issue in July Patch 2021 where stuttering started happening. 
My PC SPEC:
Ryzen 7 3700x
RTX 2080Super OC
Ram (8x2)GB 3200Mhz
SSD Nvme 500GB

Every game runs smoothly except BDO... Below here is what hapening to me. 
https://www.youtube.com/watch?v=OBdudA9YTS4&t=70s