Submitted by cmichel
The 3-path hop in VaderRouter._swap is supposed to first swap foreign assets to native assets, and then the received native assets to different foreign assets again.
The pool.swap(nativeAmountIn, foreignAmountIn) accepts the foreign amount as the second argument.
The code however mixes these positional arguments up and tries to perform a pool0 foreign -> native swap by using the foreign amount as the native amount:
All 3-path swaps through the VaderRouter fail in the pool check when require(nativeAmountIn = amountIn <= nativeBalance - nativeReserve = 0) is checked, as foreign amount is sent but native amount is specified.
Use return pool1.swap(pool0.swap(0, amountIn, address(pool1)), 0, to); instead.
SamSteinGG (sponsor) confirmed 
