Mathcad giving different answers for the same input in two different worksheets

I am solving a problem of beats in the Mechanical Vibrations course.  The problem is that Mathcad on one sheet gives a correct answer while on the other worksheet gives a very strange thing. There are no variables above or below in these files. 

I have run the recalculate command button multiple times but the answer is the same. I think there are some garbage values that it is collecting. My question is how to solve this problem and told Mathcad to forget everything and do the thing from start.

The right program is:

And, the wrong plot is:

I have also attached the files. If anyone knows why Mathcad does this and how to solve this problem please let me know. I would be happy to have your kind suggestions.