i know this is an old topic and you have probably solved it yourself already. I just had the same problem with the ofxOsc-Addon and the Arduino OSC-library. Basically the Arduino side doesn't support OSC-Bundles. The '#bundle' you get is the header for an osc-bundle (see http://opensoundcontrol.org/spec-1-0). The arduino-library interprets this as the osc-address wich is not correct.
ofxOSC for some reason creates OSC-Bundles even for simple messages. This is in ofxOscSender.cpp, ofxOscSender::sendMessage(). So if you comment out line 82 & 84 it will stop doing that. But as i don't know why every message is packet into a bundle in the first place, i'm not sure what other implications this will have. BUT it will make it work with the arduino (Z_OSC library, https://github.com/djiamnot/Z-OSC in my case).
void ofxOscSender::sendMessage( ofxOscMessage& message )
static const int OUTPUT_BUFFER_SIZE = 16384;
osc::OutboundPacketStream p( buffer, OUTPUT_BUFFER_SIZE );
// serialise the message
//p << osc::BeginBundleImmediate;
appendMessage( message, p );
//p << osc::EndBundle;
socket->Send( p.Data(), p.Size() );