OpenMPT interprets E6x like ProTracker would, and the infinite loop behaviour is correct in that case. Sadly there are many different trackers used to write MOD files, all with different behaviours and it's technically impossible to find out which one was used to write a MOD file. I guess we could disable ProTracker behaviour for E6x in case the file has more than 4 channels but that will require a lot of testing if it breaks other modules.

I have modified some playback behaviour for MOD files in r12985 so that they behave more like XM files if the MOD file is not a 4-channel file within the Amiga limits. Hopefully it doesn't break other multi-channel MODs! The new build can be downloaded within a few hours or so from https://builds.openmpt.org/builds/

PS: A single module not being played correctly is never a reason for setting the issue priority to "high" or severity to "major". Those would be applicable if e.g. the application crashes when playing a module, but not for a playback error that only affects a handful of files.