I have this problem since 0.16.0, never had it before that.
I do alt-tab alot to go to my second monitor, but before 0.16 that never was an issue
The only mods I run are RSO and ore-eraser which I don't think have any impact on this issue because I've used these mods for quite some time.
I added the save file of the map I use in case you need it.
My graphical settings:
![Image](https://forums.factorio.com/images/ext/61dc8c619850f9cd6b4a7be69eb6e141.jpg)
I also don't think my PC specs are the problem here but anyway:
Processor Intel(R) Core(TM) i7-5820K CPU @ 3.30GHz
Video Card NVIDIA GeForce GTX 980
RAM 16 GB
This is the "time usage" tab when everything is running OK:
![Image](https://forums.factorio.com/images/ext/6f3ef2b91493422b20e078e38214fed2.jpg)
So the actual issue:
Here you can see that sometimes the fps AND ups drops to around 40 while my base is not large enough by far to dip under 60.
![Image](https://forums.factorio.com/images/ext/8352cfb769de32d48f55a7daf23b2ebb.jpg)
Sometimes it even goes to 30 fps and ups...
![Image](https://forums.factorio.com/images/ext/e01d959c45110cbb2baa92e3527d0aee.jpg)
![Image](https://forums.factorio.com/images/ext/ed4ed2273a3308938c71758078cf048e.jpg)
It can also happen that the fps dips to 30, but the ups stays at 60.
![Image](https://forums.factorio.com/images/ext/4e0c8f1514edb577041dd51a1963a03e.jpg)
I will do my best to give more information if needed. I hope it can be fixed, cause it can get quite annoying sometimes.
EDIT: some fixes