Tesla claims it paid Hoerbiger, which makes hydraulic lift gates, to develop the vertically rising side doors on its Model X after a competition with several other companies. But between February 2014 and May 2015, the company couldn’t produce a prototype that passed Tesla’s engineering standards. According to the lawsuit, prototypes from Hoerbiger leaked oil and sagged or produced excessive heat, causing them to stop working. Hoerbiger couldn’t be reached for a response Tuesday afternoon at its offices in Auburn, Ala., and Schongau, Germany. “We were forced to file this lawsuit after Hoerbiger decided to ignore their contracts with us and instead demanded a large sum of money to which they are not entitled,” a Tesla spokeswoman said in an email. “We will vigorously prosecute this case.” According to the lawsuit, Hoerbiger is seeking additional payments from Tesla for the work it says it was promised. Tesla disputes that it owes the company anything more than the $3 million it paid for prototype parts and engineering. In May 2015, Tesla ditched that company’s design and built an electromechanical door system and hired a new supplier, according to the lawsuit. “Tesla incurred millions of dollars in damages, including, but not limited to costs of re-tooling the entire vehicle in order to support a different engineering solution,” the lawsuit said. In addition, Tesla had to pay the new supplier a premium to rush out a workable solution.