TRAXX electrical locomotives

The prototypes
The Bombardier TRAXX family of locomotives are a series of mainline locomotives built by Bombardier Transportation in both freight and passenger variants.
The acronym stands for Transnational Railway Applications with eXtreme fleXibility. The earlier classes were DBAG 145 and 146.
The production of 200 units built between 2001 and 2003 for DBAG were classified as DBAG Class 185. A further 57 units were built for various European leasing companies as Class 185.5 For the railways of Switzerland another 35 units were produced for SBB Cargo (Re482), and 20 units for BLS AG (Re485). The Swiss locomotives are identical to the German versions except in details such as pantographs (2 more, with smaller contacts for running in tunnels) and Switzerland specific safety systems in addition to the German systems.
The models
Märklin produced Models 36850, 36851 and 36852 (and others) with the liveries of DBAG, SBS Cargo and BLS respectively. These were relatively cheap models and were designated "Hobby". They had only one function - lights on/off but they had digital decoders. I bought them because I wanted to expand my digital fleet quickly at that time (circa 2005). Nowadays, I want to buy only MFX locomotives.
The problem
I encounter a perplexing problem - on my layout which has a mix of C-tracks and M-tracks, the DBAG model runs happily and without problem. The SBS model always derails at a particular point (M-track turnout) on the top level (L3) and the BLS model always derails at a specific point (M-track turnout) on the bottom level (L2). WHY?? They are IDENTICAL models !!! So why should they behave differently? THIS IS FRUSTRATING - WHO EVER SAY THIS IS A STRESS-FREE HOBBY????