What to do to avoid fictitious errors in worksheets created with mathcad-prime-3.1?

Hello everyone, I have this problem with mathcad-prime-3.1: I import  data, with the use of READEXCEL, from a file with extension .xlsx. I made some changes in the argument of READEXCEL, then I deleted the changes. Nevertheless, many variables are no longer recognized. See example in the image below. At first, I modify the β1 index, then I delete the change and the error disappears. How to avoid this "strange phenomenon."

Thanks for your kind attention.

With best regards

FM