That related to how the rows are being indexed in your loop - rather than looping through rows, it is looping through the text in one row that has been selected - this is not normal, but perhaps there is something odd going on with the combination of nested loops. For your loop2, you need to pop a value into a variable (currentRow = arr.pop()), and then use it in an array to index the rows e.g., [currentRow, currentRow].
Take a look at the link, and see if it is working as it should. https://run.pavlovia.org/dvbridges/test_kuhne/html/
If so, download the repo here