ORA-12805: parallel query server died unexpectedly

OS: MS Windows 2012 R2

DB: 12c Enterprise Edition Release 12.2.0.1.0 - 64bit

I am getting below error message while running a schedule job through Oracle Data Integrator 12.2. This job runs a lengthy query joining 10 to 12 tables every morning around 3am (non peek hours). Earlier data was slightly less and it was running fine but from last 6 months it has starting giving error without giving any output. The error is not consistent as sometimes it succeeds as well. However most of the days of week it throughs error after running for around 50 minutes. (like 1 days succeed, 6 days error, randomly no fixed days of week)