99 626 Hard shift in 2nd with 3 transmissions

We purchased a 99 Mazda 626 4 cyl from CarMax. It would shift hard into 2nd gear from day one. Eventually, the transmission burned up (we found out that the 99 4 cyl has a Ford transmission that is too small for the car and the "fix" was an external cooler). We now change the transmission fluid with each oil change, have an external cooler and an external transmission filter. One mechanic said the filter inside the transmission gets gummed up and can cause transmission failure as well. There is no way to replace it without taking the whole transmission apart so he suggested the external filter...so far..so good. But..back to the shifting.....

We had a rebuilt transmission put in. It too shifted hard into 2nd gear. That transmission leaked so they replaced it under warranty. The 3rd transmission and still it shifts hard into 2nd gear.

I just don't see how 3 transmissions can have the same issue. Any ideas? Maybe it's not the transmission?? If not..then what?

If it's the same shop, they probably tried to just fix the problem and claim it was replaced under warranty. It may be a sensor on the transmission that is bad, or something wrong with the computer, but with these things, it could literally be a hundred different problems.

Personally, I'd just get rid of the car. I have a 98 that's already eaten a transmission and an engine and it's only getting worse.