Question: For a particular lead, if today, lead fills the form at a landing page where UTM parameters of "Source Campaign is "Test 1" and 2 days later, he fills the form at a different landing page where the UTM parameters for the "Source Campaign is "Test 2" what value will reflect in "source campaign" field? Will it update to Test 2 or not?
Answer: For the above scenario, for a given lead, the Lead Source, Source Medium, Source Campaign will be tracked only in the first instance or the time lead fills the form. In case of the second instance only the page visit or UTM values gets tracked in the URL, however, values don't get change or updates against the existing lead.
In this case, since the mentioned lead already has the value, hence when second-time Source medium didn't track against the lead.
Work-around: In case the user wishes the value to be updated, you may create a automation based on page visit and then update the source medium value.