Mut constraint error on Raydium

After much struggling and switching between 100 LLMs, I have finally found the issue.
The issue was that my contract itself was generating input account types from an outdated IDL of Launchlab, where writable: true was not set.
I was of the assumption that it does not matter as I thought Solana would simply forward the accounts without touching their properties.
After I updated the IDL and regenerated the contract, all tests seemed to pass.