Check if either balance_repl.js or sharding_rs2.js would be affected by making their mongod secondaries unelectable so as to prevent stepdowns. Or perhaps removing the secondaries if they are unimportant.
The mongod stepdown is causing moveChunk to fail, and ultimately the tests to fail, in the sharding_continous_config_stepdown suite.
From the test failures, it appears that the heartbeat is received by the primary mongod, but not executed for some time, during which time the primary decides to step down because it hasn't heard from anyone. Or the secondary doesn't hear from anyone and runs for election