broken on paritytech/substrate

[sam0x17]

I've used cargo-docs for quite some time successfully for the work I do on https://github.com/paritytech/substrate however recently this stopped working. Running cargo docs on a recent version of master will result in thousands of cascading errors such as:

[INFO] fingerprint error for pallet-root-offences v1.0.0-dev (/Users/sam/workspace/substrate/frame/root-offences)/Doc { deps: true }/TargetInner { ..: lib_target("pallet-root-offences", ["lib"], "/Users/sam/workspace/substrate/frame/root-offences/src/lib.rs", Edition2021) }
[INFO]     err: target configuration has changed
[INFO] fingerprint error for pallet-scored-pool v4.0.0-dev (/Users/sam/workspace/substrate/frame/scored-pool)/Doc { deps: true }/TargetInner { ..: lib_target("pallet-scored-pool", ["lib"], "/Users/sam/workspace/substrate/frame/scored-pool/src/lib.rs", Edition2021) }
[INFO]     err: target configuration has changed
[INFO] fingerprint error for pallet-session-benchmarking v4.0.0-dev (/Users/sam/workspace/substrate/frame/session/benchmarking)/Doc { deps: true }/TargetInner { ..: lib_target("pallet-session-benchmarking", ["lib"], "/Users/sam/workspace/substrate/frame/session/benchmarking/src/lib.rs", Edition2021) }
[INFO]     err: target configuration has changed
[INFO] fingerprint error for pallet-staking-reward-fn v4.0.0-dev (/Users/sam/workspace/substrate/frame/staking/reward-fn)/Doc { deps: true }/TargetInner { ..: lib_target("pallet-staking-reward-fn", ["lib"], "/Users/sam/workspace/substrate/frame/staking/reward-fn/src/lib.rs", Edition2021) }
[INFO]     err: target configuration has changed
[INFO] fingerprint error for sc-consensus-manual-seal v0.10.0-dev (/Users/sam/workspace/substrate/client/consensus/manual-seal)/Doc { deps: true }/TargetInner { ..: lib_target("sc-consensus-manual-seal", ["lib"], "/Users/sam/workspace/substrate/client/consensus/manual-seal/src/lib.rs", Edition2021) }
[INFO]     err: target configuration has changed

etc.

To reproduce, simply try running cargo docs on master on that repo and you'll see what I mean.

Notably this only happens when running cargo docs whereas running cargo doc works just fine.