Yes, trigger once is a common mistake. Sometimes, it’s used too often and other times not enough.
Another one is states. A lot of people create a domino effect by using an event that changes a value which makes the next condition true and undos the first action.
example:
Variable = false set Variable to true
Variable = true set Variable to false
See:
How to make toggleable states
Another one is using AND where it’s not needed.
Events all need to be true by default. The only place you need an AND is inside an OR
One of these is true (OR)
----Mouse is down
----All of these are true (AND)
-------Mouse is Released
-------Mode equals true
Either the mouse is down or the mouse is released and mode is true.