MongoDB 4.0->4.2 Prep: WiredTiger migration out of memory

I am prepping for a MongoDB upgrade. I started by upgrading our staging environment. It mimics our prod environment – both are set up as 3-member replica sets primary-arbiter-secondary.

MongoDB was at 3.2 and I am attempting to upgrade to 4.2. I got up to 4.0 and am now stuck on the WiredTiger migration and also returning to working MMAPv1… I started with the secondary server trying to migrate to WiredTiger. I got to the step to recreate the data files by starting the initial sync. However, it is always failing with an out of memory error in the same place. And to top it off, when I tried to put it back to how it was by switching back to MMAPv1, it also gets an out-of-memory error on the initial sync.

Can anyone offer some advice on how to fix this?

I am using AWS EC2 instance t2.micro with 2GB RAM. Here are the databases stats:

Thanks in advance!