UPS getting worse

[DepletionMeeple]

I know that this is not a very new topic and I already read through various threads regarding this here and on reddit, but still have a lot of unanswered questions.

The problem is, that my megabase was really belt-based with about 400k blue belts, 50k pipe, 100k inserter, 1 GW coal steam power (rest was solar) etc. - well not the type of factory I would build again, but it was running and it was 100% automated. UPS(and FPS) were about 40 - so rather good for that kind of design.

Now I started to build an even bigger factory completely train/bot-based and modular. I stopped rockets from my previous base and just used my previous base as a material production factory to built up the new base.

But as soon as I started building the new factory, UPS decreased permanently. It is now at about 25 and going down with every thing I will build.
The elements of the factory built so far don't have huge amount of belts (in total about 2-3k), there are no big factory arrays yet (just melting with a lot of beacons - about 2k melting with 6k beacon), storage is made basically out of yellow storage chests (as I play vanilla, no warehouses).
In addition, the map I'm playing was set to "enemies don't attack" - so I guess that path calculation for biters due to pollution shouldn't be a big issue then.
So far I can see, nothing that really should have a massive impact on UPS, but unfortunately, it does. The only thing, that really could have an impact is, that there are a lot more robots now. For mining, melting, storing ore and metal, there are on average 20k-30k robots flying and about 100-200 trains additionally moving. But as the new factory is modular, there is no huge spanning logistic network, but rather small modular outposts.

So same stats for my performance (unfortunately, I don't have stats for the 40 UPS map):
Active Entities: 500k
Chunks with entities: 70k
Game update stats:
circuit: 3.5
transport lines: 3.0
entity updates: 20
electric network: 3.7
trains: 0.6
rest is not worth counting

obviously it is entity update

Now my questions:
- As I mentioned above, I don't expect path calculation for biters due to pollution being a big problem in my case. Am I right with that? To verify, I even eliminated ALL enemies in about 15% of the discovered map without any notable effect. Furthermore: Is the time for biter path finding shown under "path finder"? If so, this value is about <0.01
- What exactly is transport lines? I thought that caluclation duration for belts would be subsumed at entity update?
- Is there a possibility to calculate entity update/circuit networks etc. for a single outpost? Just like: give me values for that 500 chunks only?

Additional problems I noticed: UPS goes extremly low if running (or driving by train) through a wood - I have to zoom very close then, otherwise it drops to 5-10 UPS. And every 2-3 seconds, the whole games freezes for about 20-30ms - so like lagging, but only every 2-3 seconds. Like 0 FPS for a short time. It's just nasty but nothing that really is making the game unplayable.
And if relevant: Of course, my CPU is always running at 100% (on one core) with about 6-8 GB RAM used for factory. As FPS always equals UPS, I don't expect the graphics card to be a problem.

So, if one is willing to help, would be very nice. If I will continue without dealing this problem, it will be unplayable before the new factory is ready and the old one can be deconstructed.

[darkfrei]

You can delete unused chunks with this mod
https://mods.factorio.com/mod/DeleteEmptyChunks

[Klonan]

Can you attach your save game?

[Jap2.0]

What's the time for render preparation, and does that peak in forests?

[Zavian]

What's the time for render preparation, and does that peak in forests?

I would also watch the flip time, and whether that rises in forest. (For what it is worth, I've seen frame rate drop in heavily forested regions. I'm pretty sure it is related to number of item that need to be draw, and to pixel overdraw).