Bundles are not necessarily committed to the DA in-order, even though the current code assumes this. It simply returns bundles in the order they're completed. The solution is to check block numbers contained within bundles and buffer blocks until the next consecutive block is found. However, since the very first bundle we fetch could be out-of-order as well, we might need to look backwards as well, besed on some heuristic. In particular, great care must be taken on restart situations, where we have processed everything up to a certain block height (on either chain) and we wish to resume synchronization from there.