We're getting the same issue on one of our Windows Servers (2012 R2 with 64GB RAM). It only happens occasionally, like once a month.
If support from SyncDeK or FileMaker doesn't come through, my proposed solution would be to write a script that checks for the process fmxdbc_listener.exe and then restarts it if necessary. Could probably use:
fmsadmin RESTART XDBC