Check for a Transmission Control Module first and foremost
This computer brain is located behind the fuse panel and can be checked for malfunction. Most of the diagnostics refer to this as a TCM problem is all of the people working in a transmission repair confuse the computer as being a part inside the transmission. I discovered this on my own and found out that no one would diagnose correctly. They only want to rebuild your transmission for upto $5,000 or better yet while we paid for the breakdown of our transmission they actually replaced with a Golf transmission and gave back to us with same problem they misdiagnosed. Transmission was slow going into reverse well it was a TCM (computer) and we paid thru the touch for the miss-representation which was carried out in two other locations. $1,500 plus $100 diagnostic plus $3,500 plus another $400 until we decided to just put in a used transmission for $2,500 plus $500 to change the front boots as they had been tampered with also, but this was difficult also as we discovered the first company changed the transmission out with a goff transmission with no disclosure they stole our transmission. Such crooks when all that was needed was the TCM a $100 part a $250 install and reprogram. Do not be fooled as we were. This was on going since April 2019. If you need a transmission buy a used one and have it installed.