Solution:

It seems that you are trying to control the same D/O bit with two different tag. Since the VisiDAQ will scan the tags in your strategy one by one, if the output value is different in those two tags, it will cause the output flicker. The best way to solve this problem is control each D/O bit with one tag. If there are more than one element to decide the state of D/O bit, you can make a judgement by taking use of 'User program tag' then output though one single tag.