postgresql crash in master node with streaming replication
If that crash is repeatable, you probably have data corruption in your table. If the crash is not repeatable, the cause could be faulty memory.
At any rate, the odds are good that your hardware has problems. That would not surprise me, if you are as negligent with hardware maintenance as you are with software maintenance (9.4 is out of support).
Use reliable server grade hardware and keep your software versions reasonably recent.