Based on my research, prompted by finding the machine filled with mold/fungus, yes. It's a container filled with moisture, locked behind a water tight seal, with layers of soap; more or less the perfect conditions for mold. It's a prevalent enough problem that there were rumblings of a class action; though it's America, so take that with a grain of salt.

I'm not sure if there's another variable that would lead to different experiences. Like you say perhaps it's dependent on water. Water in my area is very hard. Perhaps it depends on soap. Some detergents contain borax which is particularly good at killing mold in this situation. Maybe some machines are better at draining and/or airing out when not in-use. Frequent use of bleach may help.

The previous owners of the machines were not ... the best of tenants. Perhaps they did something else to compound the issue. Excessive soap is an additional culprit.