My power query editor freezes when adding a customized column

Hi!
The issue is that I got 4 excel files, I create a new table based on these 4 tables, I run transpose and then add a new custom column and....it crashes!!
1st: 

2nd: Transpose:

3rd: Add custom column: it crashes. Maybe it is amatter of size after transposing?

Many thanks in advance for your help!!!!