Suppose you are getting your oil changed or your taxes done or getting vaccinated. Furthermore, suppose that you pick up multiple clues that one of the people providing the service is "under the influence". Does that present a moral dilemma if they seem to be sort-of, kind-of be doing a barely-good-enough job?
"What kind of clues?" you ask.
MULTIPLE clues. Patterns of clues.
Bobbling dexterity tasks they have done a thousand times before. Not just one task, but multiple tasks.
Losing paperwork in the eight steps between one station and the next.
Running over customer property with the wheels of their mobile equipment.
Hyper-focusing on some of the tasks to the detriment of others.
Getting tangled up in hoses, tubing, wires that is the same today as it was the yesterday and for the last year they were working.
Holding a work-piece in one hand while spearing with the other when a prudent operator would put the work-piece on a table, secure with one hand and stab with the other.
When "goofs" are called to their attention they have a glib, practiced, pre-canned "explanations" instantly ready.
Being overly loud and shatteringly cheerful.
Volunteering that they had "bad luck" with the last customer, too.
What can "under the influence" mean?
It can mean that they are drunk or intoxicated.
The drug can be easy to detect (alcohol) or undetectable (most synthetic cannabinoids).
"Under the influence" can also mean that the user is suffering withdrawal symptoms or is hung-over.
Finally, it can mean that the user is NOT under the influence of a prescription drug they need to function in the work environment. If a person has severe Attention Deficit Disorder and they are not taking their Adderal...they are out-of-standard. Or maybe they stopped taking their anti-psychotic like Risperidone
Why would somebody not take their Adderal? Well, it has street value and maybe they sold it to buy something more to their liking. Or perhaps they are saving it up for a big party so they can stay awake all weekend.
The supervisor's dilemma
Given the number of undetectable drugs and the possibility of the issue being caused by a hang-over, the ideal answer would be if the supervisor could observe the employee's performance and discipline based on observed behaviors.
The advantage of "writing-them-up" for substance abuse is that it is considered a disability in most states and it gets handled by Human Resources. They blow a 0.14% on the breathalizer and it is a done-deal.
The disadvantage of writing-them-up for performance is that the employee (or former employee) will challenge the discipline claiming the observations were subjective. Unfortunately, "jobs" are treated as if they were the employee's property by many courts and a high level of proof is often required to make discipline stick.
Back to the consumer
Yeah, it sucks. But report it anyway. Don't be stupid. Wait until after you oil is changed or your tax data is stored or your shot has been given. Then find a supervisor and discretely share the evidence you observed.
Share your observations, not your conclusions. Don't make conclusions although it is fair to offer "Intoxication" as a possible root-cause.
Tell the supervisor you are not making accusations but that you have a responsibility or obligation to exercise due-diligence to call this matter to the organization's attention. The supervisor should be OVER-JOYED that you called the issue to their attention privately rather than smear it across social media.
There is no guarantee that the supervisor will do anything about it. I worked in one factory where one area, one shift was entirely active alcoholics and they covered for each other. Go on a one-week bender? Nobody on first shift would ever hear a word of it. I suspect that crew on second-shift would kill for the management who enabled them.
However, it is more likely that the possibly-intoxicated employee has been a perennial thorn in the side of management and most of the employees. Your speaking up is an important part of resolving the issue.