Using v19.60.0008, there seems to be a recent issue that causes the input() multi-line to not continue the script when OK is pressed, instead scripts are aborted at that point, input() single line seems unaffected though.
eg. script to reproduce:
results in no message box being shown. The issue is also present where you have used the same control natively within XY, eg. Edit toolbar button dialog left/right click action multi-line etc.