Just to update, I couldn't really find a workaround for the EN issue. It is a very mixed bag apparently. I spoke to 6 agents over several days and some said they have a few issues with inventory/ access vs. M&M site and examples can be EN coded flights but also LH "train segments" operated by DB.

Beats me, and I finally gave up and plan to drive instead (or if needed buy standalone MUC-FLR-MUC). For LH, LX flights there was a good match between online and offline availability though the agents surprised me at times seeing something I could not see online or vice versa seeing only 1 seat when M&M shows 2 (all was for Biz). Anyways, definitely YMMV. Cheers