const auto txs_ptr = block->transactions_ptr();

include/bitcoin/node/impl/chasers/chaser_organize.ipp

@@ -125,6 +125,7 @@ void CLASS::do_organize(typename Block::cptr block,
     using namespace system;
     BC_ASSERT(stranded());
 
+    // shared_ptr copy keeps block ref in scope until completion of set_code.
     const auto& hash = block->get_hash();
     const auto& header = get_header(*block);
     auto& query = archive();
@@ -564,6 +565,7 @@ code CLASS::push_block(const system::hash_digest& key) NOEXCEPT
     if (!handle)
         return error::organize15;
 
+    // handle keeps the block reference in scope until completion of set_code.
     const auto& value = handle.mapped();
     return push_block(*value.block, value.state->context());
 }

src/protocols/protocol_block_in_31800.cpp

@@ -351,8 +351,11 @@ bool protocol_block_in_31800::handle_receive_block(const code& ec,
     // Commit block.txs.
     // ........................................................................
 
+    // This must not be a reference to the shared pointer, as otherwise the
+    // shared_ptr may be taken out of scope before the tx write completes.
+    // set_code() uses weak references to many elements of the transaction ref.
+    const auto txs_ptr = block->transactions_ptr();
     const auto size = block->serialized_size(true);
-    const auto& txs_ptr = block->transactions_ptr();
 
     // This invokes set_strong when checked. 
     if (const auto code = query.set_code(*txs_ptr, link, size, checked))