Affected version: 26.4.2 (confirmed still present in 26.5.1)
Component: com.arcadedb.serializer.JavaBinarySerializer

Summary

The writer increments properties.size() as the property count at the start, then skips writing the size/payload bytes for properties where propValue == null or where the type cannot be inferred (type == -1). The reader iterates propertyCount times and reads UTF + int + bytes for each — so a single skipped property desyncs every subsequent read.

Code

engine/com/arcadedb/serializer/JavaBinarySerializer.java:57–86, 123–129

out.writeInt(properties.size());                        // count includes every entry
for (Map.Entry<String, Object> prop : properties.entrySet()) {
  out.writeUTF(propName);                               // always written
  if (propValue != null) {
    …
    if (type == -1) { log.warn(…); continue; }          // size/payload NOT written
    out.writeInt(buffer.size());
    out.write(buffer.getContent(), 0, buffer.size());
  }
  // null values: size/payload NOT written either
}

// readExternal:
final int propertyCount = in.readInt();
for (int i = 0; i < propertyCount; i++) {
  final String propName = in.readUTF();
  final int propertySize = in.readInt();
  final byte[] array = new byte[propertySize];
  in.read(array);                                       // see issue #10
  …
}

Impact

Any document with a null-valued or un-serializable property deserializes into garbage (wrong property names mapped to wrong bytes) or throws somewhere downstream with an opaque message.

Suggested fix

Filter the map down to serializable, non-null properties; write the filtered count and only filtered entries.