thanks all for the messages
following was the screenshot from a previously backed-up flow, the current version already have all the variables and loop removed. this version has 2 Boolean variables, hence you will see the 'or' in the condition. (note: condition 4 is within condition 5, which is added after the 'do until' condition failed)


I have removed the 1 variable (the original post) and 'or' to try to isolate the problem but to no avail. the variable itself is not re-evaluated in the 2nd iteration (action failed), but somehow it returns 'true' is able to proceed with the 'true' case's connectors, even when it failed the additional condition that I include to re-test the condition
what are the best practices in using the 'do until' and 'condition' connectors?