Is it possible the txns are being prematurely deleted in this case: dgraph/draft.go at 5429202ea764975fc62bfc2683afedf312c0cf0e · dgraph-io/dgraph · GitHub
I am wondering if this txn.Cache().Deltas() is length 0 for every txn in the batch then deleteTxns() would run and if applyMutations() needs to look for that txn then it explodes. This would explain why it repeatably explodes after coming back up and reading the wal.
c := txn.Cache()
...
num := len(c.Deltas())
...
if num == 0 {
continue
}