Crazy unexplained artillery ???

[Jobu8888]

I'm playing a CMFI quick battle. Me US attacker, opponent Germans. During turns 5-15 there was some artillery landing on my left near my advancing troops that looked like sporadic spotting rounds, but no following barrage; and on my right just about on top of the expected German first line of defense there has been a multi-turn and pretty heavy barrage, of at least 105mm variety.   All of it coming from the German side of the map = German artillery, based on the direction of the incoming shells. And also based on the fact that I have not called in artillery yet.  But my opponent insists it's not his artillery either, and I have no reason to think he's messing with me because we've played plenty of games in the past and neither of us is that serious that we would try deception or whatever.   Also he would certainly not have shelled the absolute #^%$ out of an area where he knew only his troops could be located, and kept up the shelling for multiple turns.   So both of us are certain we didn't call in the artillery.   So I ask what the hell??   Has anyone else ever experienced anything similar?