In a previous job I worked for a company whose product needed some entropy on startup. It originally read from /dev/random. But then one of our customers reported that the product was hanging on startup, just after installation. It turned out that they had installed it into a freshly built VM (not a cloned one, I guess) and the read from /dev/random was waiting to accumulate enough entropy to return. (We changed it to use /dev/urandom instead, which is not entirely satisfactory, but at least prevents hanging in this situation.)

While this is not exactly the scenario the OP is describing, it's another thing that can go wrong with /dev/random and VMs.