Electric automaker Tesla (TSLA) is working to improve its self-driving system to fix a braking problem. Tesla stock fell 4.42% on Wednesday to close at $589.89. CEO Elon Musk tweeted that the revamped autopilot software may be released in the next few months. However, the executive cautioned that it is difficult to accurately predict the timing of a new product's availability. The coming update is expected to bring many advancements to Tesla’s self-driving feature. Notably, it will resolve the problem of Tesla cars on autopilot randomly applying the brake, particularly when driving under an overpass or bridge.