MDS was also known for broken cranks (two in our club). In diesel operataion, the crakshaft is the mainstay. If shafts fail in glow operation, no way will they hold up after diesel conversion.
This apart from the several small quality control items that added up to very haphazard fitness for use of the engine.
True, SOME Russians make SOME of the best diesels in the world. That does not mean that ALL Russian engines belong to that class.