Arranger Event mutes in one bar

My project has an Arranger Track. One of the Arranger Events consists of 3 bars and is repeated 5 times in the project. The Arranger Track (and thus 5 times the 3-bar Arranger Event) replays without a problem.

To export to an MP3, I “flatten” the project. However, in this flattened version, the 3rd bar of the 3-bar Arranger Event is not played on a certain track (the other tracks have no problem), but this only happens the 2nd and the 5th time the Arranger Event is played.

I tried everything I could think of: “flattening” in all possible configurations, checking if there is no control track (like “expression” or “volume” active), disabling “read” for the track concerned, even deleting the entire 3-bar track event in the 2nd Arranger Event and rewriting it manually!