When I try to load a save file I get this error:

The mod Spidertron Generator Project (1.8.1) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event SpidertronGeneratorProject::on_script_trigger_effect (ID 173)
__SpidertronGeneratorProject__/control.lua:296: attempt to call local 'script' (a nil value)
stack traceback:
    __SpidertronGeneratorProject__/control.lua:296: in function <__SpidertronGeneratorProject__/control.lua:294>

Uh oh, that's probably the new scripts not playing nice when a previous version of the mod was installed in a save.
For now, please use the last pre-1.8.0 version, I'll see if I can make the scripts save-compatible.

Can you try the new version? I guarded against non-existing scripts before the mod could be initialized.
Thanks a lot for the bug reports, by the way, they really help me keep track of what things I should pay attention to!

I was able to load in now.
I do have a non-critical error after loading in though:

[PlanetsLib]: Warning, suspected unresearchable technologies: [Technology: Flying combat heavy ship] due to hidden prerequisite 'spidertron'. PlanetsLib has mod settings to help you unlink them or disable this warning.

The mentioned technology comes from Lex's Aircraft

I don't know if this will actually cause any issues, but thought I should let you know, just in case.

I also just noticed a different potential issue with your tech:
It seems to me like your auto-tech is looking for every technology required to make certain materials. This does, for example, lead to me needing to visit Cubium just to get Cube Mastery 2, simply because it unlocks a unique recipe for making Engines as well as Pelagos to get Engine casting and the Shattered Planet to get Alternate Construction, because that unlocks a different Plastic recipe.

(This is just a tiny excerpt of the list of different planetary resource tech requirements that are needed)

The fact you could load in is a relief!
For the research, yeah that's because I hide the original spidertron research. It's good that you report this, I'll have to think of a solution. Either un-link all technologies from the original spidertron research, or keep it and insert my own stuff in there. This won't be a quick fix, though, I'll keep you posted!

About the technologies, that's exactly how my code is set up. I thought it was pretty clever at the time, and works beautifully in limited test cases, but I had no idea of just the scale of mods are out there.
I have to rewrite that part to make sure the technologies with the lowest amount of sciences are selected, because a full blacklisting table is going to be unsustainable.

Yeah.
A lot/most planet mods have unique ways of crafting/acquiring most vanilla resources, which leads to all of the planets ending up as a hard clear requirement to get access to even just basic Spidertron tech.

No worries! I've just prototyped a working science score method, which makes the techs select the prerequisites that use the least/simplest science techs (with a penalty for non-vanilla packs) and ignores the others. It works for vanilla Space Age, I'm gonna stress test with all the mods you're named and see what happens

I think the most important part is to do a deeper check for prerequisites, since a lot of the techs are trigger techs. (If you're not already doing that)

That was a good point, I have disallowed trigger techs from becoming prerequisites. In general, techs will select the lowest tech score candidate, so things should be pretty smooth and compatible from here on out.
As a funny note, during testing I noticed that the forbidden spidertron tech now requires the voidcraft uranium tech instead of kovarex enrichment, because to cumulative science cost of kovarex is larger than the penalty of 1 non-vanilla science pack. I thought that was pretty cool, and that is an acceptable result for me.

The spidertron technology logic has also been changed, if there's at least 1 technology with the vanilla spidertron technology as prerequisite, then it won't be removed. Please give it a try and see if it works!

Okay, the requirements are no longer absurd, though there are some funny quirks.
First up: New Error

[PlanetsLib]: Warning, suspected unresearchable technologies: [Technology: Forbidden spiedertron Technology], [Technology: Spider critter], [Technology: Spider ravager], [Technology: Spider engineer]  due to hidden prerequisite 'cerys-nice-try-sukaz'. PlanetsLib has mod settings to help you unlink them or disable this warning.

And due to the way you now select techs it is possible to research both the final Prime and Constructron without ever unlocking Military :) (Not entirely Prime, since Combat Spidertron tech still needs Military science)

I've re-purposed the blacklist for this, we'll see what happens. Also, for the military science, that's actually intentional, only the combat-related spider technologies explicitly get the military science pack injected if it wasn't already present.

I'm shipping stage 2 of the weapon update now also.