Considering the degree to which Tesla Inc. (TSLA - Get Report) has been a company valued, analyzed and judged based on the sales potential of mass-market cars that haven't launched yet, a major selloff on account of a slight quarterly delivery shortfall for the company's existing, costlier vehicles is a little strange at first glance. Especially since Tesla chalks the shortfall up to a manufacturing issue that has been resolved.

But the selloff becomes a little more understandable when one remembers how much has been priced into Tesla's shares following an epic 7-month rally. And a little more still when one considers how Tesla's delivery shortfall -- hardly the first of its kind -- might be stoking fears that Tesla won't hit the very aggressive production targets it has set for the coming months and years.

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After the bell on Monday, July 3, Tesla disclosed it delivered "just over 22,000 vehicles in Q2, of which just over 12,000 were Model S [sedans] and just over 10,000 were Model X [SUVs]." It added that 25,708 vehicles were produced, and said it's confident Model S and X deliveries will rise in the second half of 2017 relative to the first half provided macro conditions "do not worsen considerably."

Though up 53% annually, deliveries fell from a reported Q1 level of 25,051, and were roughly flat with a Q4 level of 22,252. They missed a consensus analyst estimate of 24,000, and resulted in Tesla just barely hitting a first-half delivery guidance range of 47,000 to 50,000. Production rose 40% annually, but grew just slightly from Q1's 25,418 and Q4's 24,882.

Shares fell 9.1% on Thurday to $319.43, and are now down 15% from a late June peak of $386.99. But they're still up 51% in 2017, and leave Tesla sporting a $52.4 billion market cap -- higher than Ford Motor Co.'s (F - Get Report) and just slightly below General Motors Co.'s (GM - Get Report) .

Tesla primarily blamed its Q2 delivery weakness on "a severe production shortfall of 100 kWh battery packs, which are made using new technologies on new production lines." It claims production was "about 40% below demand" until early June, and insists deliveries were strong after the issue was resolved.

That sounds believable enough. But one can't forget that Tesla also had a delivery shortfall in Q4 2016. That time, the company blamed "short-term production challenges" related to its Autopilot 2.0 hardware.

Likewise, Q2 2016 deliveries of 14,402 and production of 18,345 respectively missed guidance of 17,000 and 20,000. That time around, Tesla blamed challenges related to a "steep production ramp." Due to the Q2 and Q4 shortfalls, 2016 deliveries came in slightly above 76,000, missing original guidance of 80,000 to 90,000.

Tesla CEO Elon Musk.
Tesla CEO Elon Musk.

Given such a track record, not to mention the delays Tesla once saw in rolling out the Model S and X, it's easy to get why investors who have seen Tesla's shares blast off might be nervous that the latest production issues for existing cars might be a sign of things to come for the massive production ramp scheduled for the relatively cheap Model 3 sedan. Ahead of the Q2 disclosure, Elon Musk tried to reassure investors, along with the many people (possibly over 500,000) who have made deposit payments for Model 3 reservations, by stating the first Model 3 should come off the production line on Friday, two weeks ahead of plan.

Musk added the first 30 Model 3 cars will be delivered to customers at a July 28 party. He forecast production will top 1,500 units in September, and said it "looks like [Tesla] can reach" a production rate of 20,000 units per month in December. The company previously said it's hoping to reach a production rate of 5,000 units per week (slightly over 20,000 per month) "at some point in 2017."

Tesla has already backtracked a little from a goal of producing 500,000 vehicles in 2018. The company is now hoping to reach a production rate of 10,000 vehicles per week (implied annual rate of 520,000) "at some point in 2018." For now at least, it hasn't backed away from a target of reaching a 1 million-vehicle annual production rate in 2020.

Though analyst delivery estimates are more conservative than Tesla's production targets, they do still forecast a giant production ramp for the Model 3 ($35,000 starting price) and eventually the Model Y crossover. On average, analysts polled by FactSet expect deliveries to rise slightly to 26,000 in Q3, before surging to 39,000 in Q4 due to the Model 3 ramp. And they're forecast to nearly triple in 2018 to 325,000, before rising to 541,000 in 2019 and 683,000 in 2020.

It should be noted, however, that there's a lot of variation in individual estimates. For example, Piper Jaffray only forecasts 34,000 Q4 deliveries, while Evercore ISI expects 46,000. For 2018, Piper expects 273,000 deliveries, while RBC forecasts 350,000.

There's clearly a tremendous amount of uncertainty about just how fast Model 3 sales (never mind Model Y sales) will ramp. Any bit of Tesla news that will make some bulls second-guess their expectations for this ramp, or makes some shorts feel more confident about their very different expectations for the company, is likely to spark a selloff.

That comes with the territory when a company expected to sell less than 120,000 cars this year is worth more than Ford.

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