mongodb: Mongo slow start after update to 4.2.5

I have updated the MongoDB replica set, which consists of 3 members, from 4.0.11 to 4.2.5. After the update, the startup takes about 5 minutes. Before updating it was instant. It is related to the size of the oplog, because I tried the oplog crash in the new mongo 4.2 and the start was instantaneous. The maximum oplog size was 25GB, I reduced it to 5GB and the startup is still slow. Mongo db is on AWS with standard EBS disks. However, mongo worked fine until this update. Do you have any idea what a slow start can cause? Thank you.