Recently, I've started having this issue as well. My FPS drops from ~140 FPS to 10-30 FPS. It will stay there until I get away from either base. This has occurred during several matches. While I have encountered it several times, my ability to replicate it has not gone well. Replays don't seem to replicate the same performance issue.
Match ID: 3899433; Issue occurred in last 2-3 minutes of the match
Basic Specs
CPU: AMD Ryzen 5 7600X
GPU: NVIDIA Geforce RTX 4070
RAM: 32 GB
OS: Windows 10 Pro 64-bit (OS Build Version: 19045)
Steps Attempted
Note: The issue occurred after running through the steps below. Sharing them in the off-chance something sticks out/it helps
1. In the match, I checked Task Manager usage. Nothing was exceeding 60% on my CPU, GPU, Memory, etc. Attempted to still end unrelated programs to the game, but issue persisted.
2. Checked my GPU Drivers. I was initially out of date. However, the issue is still occurring on the newer drivers still. I'm currently on GeForce Game Ready Driver 560.94.
3. Checked my graphic settings. Normally, I get ~140 FPS on these settings. I attempted to lower my settings to the second option, but the issue persisted still.
4. Verified my Windows 10 installation is up-to-date. It is.
5. Restarted computer. Issue is still occurring.
6. Checked Event Viewer. The only item around the relevant time I found were these two items:
7. I've had some issues with Steam in the past year for some reason. I went ahead, opened CMD (Admin), and ran the following:
"C:\Program Files (x86)\Steam\bin\SteamService.exe" /repair