Singer's machines such as those made in 70s with zigzag are good, and durable but are not made by the original Singer company, Singer stop sewing machine business after world war 2, but some older model has continue in production up to 50s by remaining factories. It is probably of this reason that older Singer machines has been cloned legally in many countries.
The modern domestic (with exception of industrial) white plastic Singers are produce by some reputable company but some are not, regardless they are designed to be disposable, which required frequent service and not build to last.