Call to setFeatureCompatibilityVersion sometimes hangs when upgrading from 4.2 to 4.4 on sharded cluster

I've noticed that after upgrading a 4.2 sharded cluster to 4.4, the call to setFeatureCompatibilityVersion sometimes hangs. I've set a 10 minute timeout on the command and it is reached quite often.

I can't reproduce this problem all the time. It will usually take about 10s for the command to run normally. I've had cases where it reaches the 10 minutes timeout and other cases where it takes much longer than 10s but still completes within the 10 minute timeout. The logs for mongos don't seem to indicate any problem.

I'm using the latest versions of 4.2 and 4.4.