Is "doing according to one's best understanding" a protection from wrong-doing?

There are several suttas addressing the necessity in reflecting over consequences - besides our intentions - for the sake of benevolence.

From the Ambalatthika-rahulovada Sutta:

All those brahmans & contemplatives at present who purify their bodily actions, verbal actions, & mental actions, do it through repeated reflection on their bodily actions, verbal actions, & mental actions in just this way.

Thus, Rahula, you should train yourself: 'I will purify my bodily actions through repeated reflection. I will purify my verbal actions through repeated reflection. I will purify my mental actions through repeated reflection.' That's how you should train yourself.

https://www.accesstoinsight.org/tipitaka/mn/mn.061.than.html

Also, one of the five rememberances from Upajjhatthana Sutta regards the consequences of our actions:

Now, based on what line of reasoning should one often reflect... that 'I am the owner of my actions, heir to my actions, born of my actions, related through my actions, and have my actions as my arbitrator. Whatever I do, for good or for evil, to that will I fall heir'? There are beings who conduct themselves in a bad way in body... in speech... and in mind. But when they often reflect on that fact, that bad conduct in body, speech, and mind will either be entirely abandoned or grow weaker...

https://www.accesstoinsight.org/tipitaka/an/an05/an05.057.than.html

This is also addressed in the Cula-kammavibhanga Sutta:

Beings are owners of kamma, heir to kamma, born of kamma, related through kamma, and have kamma as their arbitrator. Kamma is what creates distinctions among beings in terms of coarseness & refinement...

https://www.accesstoinsight.org/tipitaka/mn/mn.135.than.html

A more thorough description of consequences is detailed in the Maha Kammavibhanga Sutta. At the end this is summarized as:

So, Ananda, there is kamma that is incapable (of good result) and appears incapable (of good result); there is kamma that is incapable (of good result) and appears capable (of good result); there is kamma that is capable (of good result) and appears capable (of good result); there is kamma that is capable (of good result) and appears incapable (of good result).

https://www.accesstoinsight.org/tipitaka/mn/mn.136.nymo.html

I cannot see how it would be possible to do any better than doing the best we can. If we do this but inadvertently cause suffering or harm then it would hardly be fair if this created bad karma.

Surely it is intention that matters, not the outcome of the action, especially since approximately all the outcomes of our actions cannot be known in advance.

The only proviso seem to be that 'doing the best we can' must involve the acquisition of knowledge, since ignorance is no excuse for wrong-doing where it is a choice.

Doing the best one can is relative to what one knows. If what you know is the method described in the Dhamma, then 'doing the best you know how at the time', if followed-up with a little review of the results will move you steadily from higher to higher and on out.

Doing the best that you can, is not a protection against wrong-doing.

Why? Ignorance, or the lack of Right View and wisdom, may cause you to commit wrong-doing, despite doing "the best that you can".

Hence, gaining Right View, and gradually improving Right View and wisdom over time, through insight, will push the boundaries of your "best effort".

In the Salt Crystal Sutta (translated by Thanissaro Bhikkhu), the Buddha taught:

'Now, a trifling evil act done by what sort of individual is experienced in the here & now, and for the most part barely appears for a moment? There is the case where a certain individual is developed in the body, developed in virtue, developed in mind [i.e., painful feelings cannot invade the mind and stay there], developed in discernment: unrestricted, large-hearted, dwelling with the immeasurable. A trifling evil act done by this sort of individual is experienced in the here & now, and for the most part barely appears for a moment.

And there you have it. For protection from wrong-doing, one should be developed in body, developed in virtue, developed in mind, developed in discernment and dwelling in the immeasurable.

The same paragraph translated by Bhikkhu Sujato here:

What kind of person does the same trivial bad deed, but experiences it in the present life, without even a bit left over, not to speak of a lot? A person who has developed their physical endurance, ethics, mind, and wisdom. They’re not small-minded, but are big-hearted, living without limits. That kind of person does the same trivial bad deed, but experiences it in the present life, without even a bit left over, not to speak of a lot.