Cross-chain routes aren’t atomic, once the bridge step has completed it can’t roll everything back if there's an internal revert. The fallback is to deliver the token that was safely available on Base (USDbC) and mark the transfer PARTIAL—so the user's funds aren’t stuck or lost.
You can find more details on our main website and its AI powered search assistant
https://docs.li.fi/guides/routing/route-availability#what-does-the-partial-substatus-mean-in-a-transaction