Hi @personal_java and welcome in the MongoDB Community 
!
MongoDB is currently in version 6.0.3.
V3.0.4 was born in March 2015 and reached end of life support in Feb 2018 according to MongoDB Legacy Support Policy.
So my first suggestion would be to update this cluster to 6.0.3 ASAP and there are good chances that your problem could just go away with the upgrade.
Are you still running on MMAPv1 or are you using WiredTiger?
Cheers,
Maxime.