Just to add to what Dan said, this sounds like a possible pressure issue which is what he mentioning with the pump. However, I have also seen on this transmission where it gets low on fluid due to a leak or just poor fluid condition and it causes this issue.
Basically it is just pulling air into the pick up rather then fluid.
This can be solved by servicing the unit, correcting any leaks and putting the correct amount of fluid in it.
Here is a guide that will help with changing the fluid which will give good info:
Below you will find the process on how to check the fluid level. You do not have a dipstick so you basically remove this plug in the pan and if the fluid is not running out then it is either low or perfectly filled. So you need to add fluid to it until it runs out of the plug. Then let it stop and replace the plug.
Take a look at the info below and let us know if you have questions and what you find. Thanks
Images (Click to enlarge)
Thursday, July 22nd, 2021 AT 7:04 PM