Once in a while this car will downshift on the freeway very hard during accelleration. The first time it happened I thought I had hit something that's how hard it is. Looking for answers I came across someone who was having a similar problem on this forum post http://www.corollaforum.com/threads/2015-toyota-corolla-l-4-speed-transmission-problem.5497/ . The last post says "Toyota fixed the problem with a transmission solenoid part no. 35230-52021". I know nothing about automatic transmissions but wanted another opinion before I spent the money to get it replaced.
Thank you!
You should have a mechanic who works on transmission to inspect it. By the way, changing solenoid is one of the least expensive repairs on the transmission, so if it is the issue, do not worry.
For anyone who stumbles on this in the future. I did a lot of research and it came down to either a solenoid or low transmission fluid so I took it to the dealer and had them drain and fill the transmission on a guess. It hasn't happened since.
Great.