BATTLETECH - Unexpected framerate drops

[tarasis]

One line summary of your issue
Unexpected framerate drops

Please explain your issue is in as much detail as possible.
Playing the first campaign mission, I am seeing the framerate drop from 60FPS, down to as low as 14fps before climbing back on.

My rig is:
i7 4790k 4.48GHz
16GB Ram
Win 10 64Bit
NVidia GTX 1080ti (driver released today - 397.31)
Monitor is 2560x1080, but playing game at 1920x1080

Game running with HIGH detail settings.

My system isn't stressing while playing. Observing with MSI Afterburner (I wasn't using it when observing the framedrops, only Steam's own FPS counter).

CPU 32% cpu utilization, 51c, 4488MHz
GPU 1342 MHz, 45c, 0%
60 FPS, 16.6ms

CPU: 26%, 62c, 4488MHz
GPU: 1557 MHz, 54c, 7%
44 FPS, 22.7ms

Added plots in followup post.

Steps to reproduce the issue
Play first campaign mission.
Get to the area with Ariel Bombardment.
See framerate tank from 60 to 14, then climbing to 40-45.

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[tarasis]

Here are two plots, GPU and CPU stats. The blue marks on the GPU are when the framerate tanks (the increase after is when I alt-tab to the desktop). CPU graphic taken slightly after as I saved the gpu portion, and then scrolled down to get the CPU stats.

As you can see the framerate isn't particularly stable. There were other drops earlier in the mission too, though none as severe.
As

 

[tarasis]

Redone graphs with framerate constrained between 10 & 70. Same bombardment, this time running off SSD rather than HDD. Made no difference. Drops to 10fps at the beginning where when I alt-tabbed out to adjust the graph scale for FPS,