Converting legacy file never was an easy task and most of the times it required a lot of rework and reformatting. When different variable styles were used in Mathcad this even gets worse.
I can confirm that the converter ignores the MC15 variable styles which makes worksheet using the same name in different styles fail.
I would call this a severe bug in the converter., but I understand that it would not be that easy to fix because Prime does not support variable styles (which IMHO it should).
So far the only solution I could think of is to rename variables which aren't formatted as style "normal" to something else manually, maybe by applying a literal index ".user1", etc.
But this would require you to still have access to Mathcad 15 to find out which style which variable is formatted in. In Mathcad 15 you could change the appearance of the various styles to different colors so they are easier to spot.
If you don't have access to MC15 I fear that you are lost because the information about the style is not available anymore in the Prime sheet. The converters annotation only notes succinctly that the math font has been changed.
Incidentally, I think that the original sheet is certainly not an example of successful design.
For example, a definition i:=3 in the visible area and subsequent redefinition k1:=i and i:=0..k1-1 does not seem particularly clever and the crowded formatting in the right-hand area also makes it extremely difficult to follow the calculations.
The erratic use of different variable styles adds to this. Nevertheless, a proper converter should still be able to handle the task of conversion.
Here an example of the conversion of a simple sheet using different variable styles. Directly after conversion we see the correct result (obviously taken from the MC15 sheet) but upon recalculation we see the mess the converter had made.
After conversion:
After recalculation:
