The Israeli start-up behind last week’s failed lunar landing says human error may have caused the spacecraft to crash into the Moon.

SpaceIL, said Thursday that its engineers collectively decided to restart the inertial measurement unit, a critical part of the spacecraft’s guidance system, following its malfunction in the lander’s final descent.

The team says the command triggered a “chain of events” that culminated in the spacecraft slamming into the Moon, otherwise “things may have been OK, but we’re still not sure.”

According to the investigation, a malfunction was discovered in an acceleration sensor called IMU. A command sent to the sensor led to a chain reaction that caused the main engine to turn off.

“The command didn’t directly cause the main engine to turn off, but rather caused the computer to restart and things carried on from there,” SpaceIL CEO Ido Anteby told reporters at a briefing.

5-6 attempts to restart Israeli moon lander’s engine failed, investigation finds

Without the main engine running as a braking mechanism, it was impossible to slow Beresheet’s speed from 1,700 kilometers per hour (1,000 mph) to 0 just above the Moon’s surface. Engineers were able to restart the engine, but by that time the spacecraft was too close to the surface to slow down sufficiently. Beresheet crashed with 500 kilometers per hour (300 mph).

SpaceIL says it will continue to analyze the fatal glitch and publish a formal assessment in the coming weeks.