Submitted by peakbolt
https://github.com/Tapioca-DAO/tapioca-bar-audit/blob/master/contracts/markets/singularity/Singularity.sol#L409-L427 
https://github.com/Tapioca-DAO/tapioca-bar-audit/blob/master/contracts/markets/singularity/SGLLeverage.sol#L81 
https://github.com/Tapioca-DAO/tapiocaz-audit/blob/master/contracts/tOFT/modules/BaseTOFTLeverageModule.sol#L79-L108 
https://github.com/Tapioca-DAO/tapiocaz-audit/blob/master/contracts/tOFT/modules/BaseTOFTLeverageModule.sol#L227
multiHopSellCollateral() allows users to leverage down by selling the TOFT collateral on another chain and then send it to host chain (Arbitrum) for repayment of USDO loan.
However, it will fail as it tries to obtain the repayableAmount on the destination chain by calling IMagnetar.getBorrowPartForAmount() on a non-existing market. That is because Singularity/BigBang markets are only deployed on the host chain.
https://github.com/Tapioca-DAO/tapiocaz-audit/blob/master/contracts/tOFT/modules/BaseTOFTLeverageModule.sol#L205-L227
The issue will prevent users from using multiHopSellCollateral() to leverage down.
Furthermore the failure of the cross-chain transaction will cause the bridged collateral to be locked in the TOFT contract on a non-host chain as the refund mechanism will also revert and retryMessage() will continue to fail as this is a permanent error.
Consider the following scenario where a user leverage down by selling the collateral on Ethereum (a non-host chain).
Obtain the repayable amount on the Arbitrum (host chain) where the BigBang/Singularity markets are deployed.
0xRektora (Tapioca) confirmed
