When trying to start the game with the latest update I suddenly get a loading error message

Failed to load mods _ particle_physics /data-updates.lua:98: attempt to index field 'unit' (a nil value)
stack traceback _ _particle-physics _/data-updates.lua:98: in main chunck

mods to be disabled:
particle-physics (1.0.1)

Is this a new issue or a conflict with another modpack?

There is no error for me, so it is an interaction with another mod. What mods are you using?

uhm it's quit a big list, is there an easy way for me to send it to you? Because it are like 350 mods

You can provide the text from the log file. I would need the lines that say "Loading mod". The location of the log file is explained here https://wiki.factorio.com/Log_file

I believe I have found them, is there a way for me to send the files?

You could put the information in a reply here. Please only include the lines that say "Loading mod" so that you don't expose unnecessary information.

I believe it's suposed to be this
25.106 Loading mod particle-physics 1.0.1 (data-updates.lua)
25.111 Error ModManager.cpp:1765: Failed to load mod "particle-physics": particle-physics/data-updates.lua:98: attempt to index field 'unit' (a nil value)
stack traceback:
particle-physics/data-updates.lua:98: in main chunk
25.152 Loading mod core 0.0.0 (data.lua)
25.426 Checksum for core: 3810281447
25.456 Error ModManager.cpp:1765: Error in assignID: recipe-category with name 'recycling' does not exist.

Source: default (utility-constants).
25.473 Info PlayerData.cpp:66: Local player-data.json unavailable
25.473 Info PlayerData.cpp:69: Cloud player-data.json available, timestamp 1760371874
25.475 Post-data load graphics options: [Light occlusion: YES]
25.753 Initial atlas bitmap size is 16384
25.754 Created an atlas bitmap (size 4096x496) [icon, not-compressed, mipmap, linear-minification, linear-magnification, linear-mip-level]
25.754 Loading 3D bitmaps.
25.762 Texture processor created (4096). GPU accelerated compression Supported: yes, Enabled: yes/yes. Test passed. YCoCgDXT PSNR: 35.83, BC3 PSNR: 33.82
25.787 Parallel sprite loader initialized (threads: 13, bitmaps: 146)
26.987 Sprites loaded
27.031 Generated mipmaps (5) for atlas [0] of size 4096x496
27.031 Custom mipmaps uploaded (117)
27.065 Video memory usage: 10.32 MB (Atlases: 10.32 MB, Textures: 0.00 MB)
27.071 Factorio initialised
27.078 Failed to load mods: particle-physics/data-updates.lua:98: attempt to index field 'unit' (a nil value)
stack traceback:
particle-physics/data-updates.lua:98: in main chunk

Mods to be disabled:
• particle-physics (1.0.1)
34.482 Quitting: user-quit.
34.718 Steam API shutdown.
34.722 Goodbye

You estimated that you are using 350 mods, but I only see 2 mods in this list: core and particle-physics. Some required mods are missing. Because those mods are missing, Factorio should have reported an error before it even started loading particle-physics. Either you did not provide the right information or your installation is broken.

I don't believe so, the reason you don't see all of the mods is because i didn't send all of them, I thought this might have been all of the relevant information, I've tried reinstalling the mod but I keep getting the same error, do you want me to send the full list?

Yes. As you may recall, the first question I asked was "What mods are you using?" because I wanted to know what mods you are using. I requested the log file lines that say "Loading mod" because all lines that say "Loading mod" are relevant. The problem is an interaction between Particle Physics and an unknown other mod. I can't test the other mods to determine which is interacting with Particle Physics if you do not reveal what other mods you are using.

well, I want to send every line that says loading mod, but this box had a character limit and because it's around 61000 characters it's not really possible to send it here, is there an alternative?

The error probably happens due to the Nexus mod, the same error happens on multiple other mods as well, due to the Nexus mod update 0.9.9.
Nexus changed the promethium science from ingredient based to trigger based, so particle physics tries to access the unit field and crashes.

Thank you. I've confirmed the error when both Particle Physics and Nexus are enabled, so we don't need to figure out how Realcubicgamer can send the full list of mods. I can handle the error by changing Particle Physics to be more lenient about other mods changing the post-Aquilo technologies.

well I'm happy it can be solved that way, the way for me to have send you the file would have been pretty tedious, thank you for you help

I have uploaded a new version that works with Nexus, and it should also work with other mods that change technologies in a similar way.