Robotics RL is brutally hard: one practitioner's list of a dozen failure modes

Scobleizer · x · 2026-09-19

A robotics RL practitioner's candid retrospective: pattern matching isn't enough. Their run improved 2% then crashed to 100% failure — the KL term too low for the learning rate, the critic's gradient too high. The physics engine was too inaccurate for grasping, tactile sensors produced NaNs, sensors made training painfully slow, and sim frequency mismatched real-world inputs raising sim2real doubts. At one point entropy was zeroed by a simple reward bug, making "do nothing" optimal for three days before anyone noticed. Add an fp32 vs fp64 replay discrepancy, plus days lost to wrong answers from their AI assistant.

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