I think these two flaws actually go hand in hand, despite seeming opposed:

1. Avoiding acknowledging doubts or weaknesses in the position you're arguing for.

2. Allowing a decision to be finalised when you remain unconvinced.

These two behaviours have different outcomes if you take 'outcome' to mean 'who won the debate'. But they're both flawed and they both come from underconfidence.

Confident engineers care about finding the best consensus. They openly entertain doubts in their own position (and happily change their position in front of others), and they also persist with the discussion until they're genuinely satisfied with whatever consensus is reached.

Likewise, I tend to give the other person the benefit of the doubt, and when one party accepts the possibility that they might be wrong while the other party professes ironclad certainty that they're right, the argument almost always goes to the latter.

These days I temper my "I'm not certain so we should investigate this" with "but you're not certain either so you're not getting out of investigating it and admitting you're wrong if it comes to that."

Yet another variation on this important theme: do not be afraid to speak up when you see areas of waste around you.

You think this or that project is not solving the right problem? Speak up. You think some key result should be achievable with fewer people and sooner than what was planned? Speak up.

I learned this recently, sharing feedback that I was concerned would sound harsh, only to fall on receptive and understanding ears. If anything I should have spoken up sooner/more often!

Your team/startup/etc. will thank you.

I have been in the same situation and I observed it happens more often when discussing with non-technical team members. What I think is happening here is that I forget how "business people" can have different knowledge and beliefs than I do. Assuming good intentions, it might be just lack of information on both sides that make us hold back and assume "they are probably on the right track". And IMHO that is good news because there are many possible paths to address this common issue.

It obviously a case of needing a balanced approach. Your comment and the parent are for two initial and opposed problems.

That sounds super familiar. One time my team lead moved a meeting one day back for a week, even though I mentioned that the meeting was important every day. When we finally had the meeting, she was mentioned that I took care of it too late. In these situations I tend to be too much 'yes and amen', and I should push back some more.