Tesla famously reached its self-imposed goal to build 5,000 Model 3 electric sedans in a week in the final week of July. The news delighted investors and showed the Silicon Valley-based automaker perhaps put the worst behind it.

But, new internal documents show not all is well with the batch of 5,000 cars. Business Insider reported Tuesday that of the 5,000 cars, 4,300 of them require reworking. That’s over 85 percent of the production run.

Each car took an average of 37 minutes to repair, according to the documents, which took a toll on plant productivity. The factory’s first pass yield (FPY), or production run of cars that do not require rework after assembly, sits at 14 percent for the 5,000-car batch. Ron Harbour, a consultant at Oliver Wyman, said a good plant will have an FPY of over 80 percent. Average plants hover between 65 and 80 percent.

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Tesla told BI that its FPY is confidential but noted rework doesn’t mean major repairs after production.

“In order to ensure the highest quality, we review every vehicle for even the smallest refinement before it leaves the factory. Dedicated inspection teams track every car throughout every shop in the assembly line, and every vehicle is then subjected to an additional quality-control process towards the end of the line,” Tesla said in a statement.

Even with the reworking time, the electric-car maker said man-hours required to build the Model 3 has dropped by 30 percent since last quarter.

[Source: Business Insider]