Is there a word (or expression) for when you can see someone doing something wrong?

Question

Is there a word or expression that succinctly describes/conveys the following:

I am watching someone perform a reasonably complex task/activity.
I can see a person doing something wrong, I know how to do it "right" from years of practice/experience, but it would take me too long to explain/train them to do it the right way (and they may not want to learn / modify their existing behaviour), so I just let them continue without causing a "fuss", but it still "bugs me" inside.

A single word would be awesome (however I expect it's unlikely). Failing that, an expression or "parable" would be good, too.
Essentially, I just want to convey this idea without telling people "you're doing it all wrong"!

Answer 1

... so I just let them continue
without causing a "fuss",
but it still "bugs me" inside.

Your situation seems like a good time to bite your tongue.

bite your/one's tongue (phrase)

Make a desperate effort to avoid saying something.

I often felt like I had to bite my tongue and take deep breaths to avoid berating them for their complete lack of common sense or perspective.

It is certainly not the kind of situation where confrontation is advisable - and that is why our seething guide bites his tongue and suppresses the urge to curse at their thoughtless conduct. Lexico

To stop yourself from saying something that you would really like to say:

I wanted to tell him exactly what I thought of him, but I had to bite my tongue. Cambridge

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He chuckled, hauled out the ironwork, and set to work hooking up the printer to the laptop. He was doing it all wrong, but I bit my tongue. I'd realized long ago the futility of telling Michael how to do computer tasks, so I left him to figure it out and want back to selling my dusty ironwork. Donna Andrews; Revenge of the Wrought-Iron Flamingos (2006)

I had to bite my tongue. I would just have said there was a dead body in the woods. It was far too complicated to explain what was actually happening. For now, it just needed something to grab their attention, to make them respond. Jon Wilmot; The Trail (2014)

As a teacher, it is hard to bite your tongue and let a reader continue reading when he or she makes a mistake, but it is the only way struggling readers will develop the monitoring system good readers already have. When a reader makes a mistake, wait until he or she reaches the end of the page, and then intervene. Timothy Rasinski; Rebuilding the Foundation (2011)

Answer 2

• A somewhat broader term you might want to use is toe-curling:

  Very embarrassing or excessively sentimental.

  I toe-curlingly had to watch him fumble.

• A good alternative is cringeworthy:

  Causing a reaction or feeling of embarrassment, awkwardness, or discomfort.

  His blundering was a cringeworthy affair.