I just changed my trans fluid, I used Tremec fluid. It is not ATF fluid, it is specifically for the Tremec manual transmissions. I had some notchy shifts when it was cold. Now it is like butter cold or hot. I have not had any issue shifting into any gear. You may want to check the reverse lock out sensor. The skip shift sensor is next to the fill plug and the reverse lock out is a little further back. Here is the link for the fluid, it is about the same price as Royal Purple.
https://www.tremec-store.com/product...smission-fluid