Investigate problem to withdraw WBTC-A from VAT

[LukSteib]

Goal

Enable withdrawal of WBTC-A from Vat

Context

We were notified by a user that withdrawal of WBTC-A from VAT to wallet yields an error (see screenshot 1 in asset section below). Reproduction of user flow via hardhat fork at blockheight of take event resulted in error (see screenshot 1 in asset section below)

Tasks

• [ ] Investigate the root of the problem
• [ ] fix problem to enable withdrawals in the future

Assets

• user's Take transaction to obtain WBTC-A in the first place: https://etherscan.io/tx/0x988cd91ed39ccb09f44cfdca82ae4dbc19221e97862ff2355ad8ba371b6a8c68
• auction link of WBTC-A auction in question: https://unified-auctions.makerdao.com/collateral?network=mainnet&auction=WBTC-A%3A225
• screenshot 1 (reported error)
• screenshot 2 (reproduction of error)

[LukSteib]

Following insights:

• the user's wallet had enough ETH funds at the time of execution in order to pay tx fees
• able to withdraw other collateral types from VAT (e.g. tested for ETH-A)
• WBTC-A uses a different gemJoin contract (ie. GemJoin5) compared to other gemJoin contracts (ie. GemJoin)
  • WBTC-A: https://etherscan.io/address/0xbf72da2bd84c5170618fbe5914b0eca9638d5eb5#code
  • ETH-A: https://etherscan.io/address/0x2f0b23f53734252bda2277357e97e1517d6b042a#code
  • the exit method is different (however seem to be the same arguments as guy is equal to usr)
• gem inside the gemJoin of WBTC-A is correct: https://etherscan.io/address/0x2260fac5e5542a773aa44fbcfedf7c193bc2c599
• one is able to trigger the exit function of WBTC-A gemJoin directly
  • this is how the problem was solved for now

[valiafetisov]

Let's create:

• A test for the WBTC-A withdrawal that fails
• Tests for most other collaterals (this can be another issue/pr)
  • you can create a json inside core/test folder where we can collect block numbers for all collaterals, eg "ETH-A": 123 (where the statistics script will help – you can take block numbers on which each collateral was taken and use the previous one)
  • you can then try to execute swap and withdraw DAI for all those auctions