Strong cryptography requires a reliable source of high-quality random data.
On some systems, the OS-provided random number generator, such as /dev/random on Linux systems, might block if there's not enough entropy available to keep up with the demand for strong random data, which can severely impede server performance. This is especially likely when running the server in a virtual machine or in a container because it's less likely to have access to the entropy stream from the underlying host system.
When running in non-FIPS-compliant mode, the server can work around this problem by using an alternative random number generator, such as /dev/urandom on Linux, that uses cryptographic techniques to ensure that it can still provide a high-quality stream of random data that won't block even when available entropy is exhausted on the underlying system. However, the Bouncy Castle FIPS-compliant random number generator doesn't support this alternative, and it's likely to block for long periods of time if the server is installed in a container or virtual machine.
This isn't a problem that's likely to go unnoticed because the server is likely to appear completely unresponsive for many minutes at a time if the random number generator blocks because of a lack of entropy. It’s likely to block for long periods of time, especially if the server is installed in a container or virtual machine.