Hi Leonard - attached here is a reconstructed version of your object (filename: Cushion_ctr_pipg2.3dm), I used a combination of "ShrinkTrimmedSrf", and then "untrim" on the 2 large sheets to get back to the original square-ended surfaces there, then drew in some lines and used Construct / Planar to cap off the sides.

So that results in a starting model like this (the attached one):




Now you can create the result you want with these steps:


Start by placing the large radius rounds in the corners - I would recommend just using Fillet for this part as well rather than attempting to boolean out a rounded corner. If you do the boolean you have to precisely align the cutting object and it will also be difficult to guarantee tangency in the result, your previous result was likely not entirely tangent in these areas, which will also tend to mess up further fillets along those areas as well.


So just select these 4 little edges like this:



And run Fillet, it looks like from your previous one you want a radius of something like 1.15 on these ones, that creates this for you:



Now select the entire object and run Fillet again and set your smaller radius of 0.19 and it will make this:



Does that handle what you need?

Also was the other one along side it a duplicate of this one, or was it different shaped?

You may want to double check my version to make sure I did not accidentally lengthen it or something like that when untrimming it and going back to the square corners.

- Michael