Dual checksig causes ReachedPrunedBranch (with a somewhat complex witness)

[KyrylR]

Project version

0.1.0

What happened?

For some reason, when using jet::bip_0340_verify twice in a row (with a somewhat complex witness), the following error occurs:

ReachedPrunedBranch(7edcef01d09b2bb34aadb9e6c3276e03120a8eb6cff1873fc36c726a41bab957)

Here: https://github.com/BlockstreamResearch/simplicity-contracts/blob/main/crates/simplicityhl-core/src/runner.rs#L37

Which is weird because this is the second call of the exec function on BitMachine, which is done here:
https://github.com/BlockstreamResearch/rust-simplicity/blob/master/src/node/redeem.rs#L437-L439

Minimal reproduction steps

See this: https://github.com/BlockstreamResearch/simplicity-contracts/actions/runs/20657575195

[KyrylR]

Issue is reproduced in this branch: https://github.com/BlockstreamResearch/simplicity-contracts/tree/fix/sig

cc @topologoanatom

[KyrylR]

Duplication of: BlockstreamResearch/rust-simplicity#333 (comment)

[KyrylR]

Code:

https://github.com/BlockstreamResearch/simplicity-contracts/blob/fix/sig/crates/contracts/src/sig_verification/mod.rs