Problems with battery pack production apparently required manual assembly, limiting vehicle output.

Battery pack production problems involving Tesla Gigafactory partner Panasonic were apparently among the 'bottlenecks' holding back Model 3 output.Tesla's third-quarter Model 3 production was less than 20 percent of the company's ambitious target. The company said output was restrained due to unspecified bottlenecks, without naming any particular suppliers.

Speaking during an earnings call, Panasonic chief executive Kazuhiro Tsuga has apparently admitted some responsibility for delaying Model 3 production ramp. Problems with automated battery pack assembly are said to have required workers to manually complete production tasks.

"This process will be soon automated, and then the number of vehicles to be produced will rise sharply," he said, as quoted by Reuters.

It is unclear if the battery pack assembly issues were the primary bottleneck or just one of several issues that must be dealt with before Model 3 volume begins to catch up with Tesla's lofty goals.