Penalties are applied to anyone who repeatedly leaves matches. Disconnecting/not loading in counts as leaving, because your team suffers as a result. Full details on Blizzard’s stance on this can be found in the Technical Support stickies: Overwatch Technical Issues, SR Loss, and Leaver Penalties
The best course of action is to avoid Competitive and play low stakes modes until you’ve figured out the issue. One of the MVPs, staff, or the community will likely help if you provide diagnostic info in the forum like I suggested above.