Twice we've had something similar happen.
Once was in the restaurant of an historic old river hotel, fairly tiny place, and my wife ordered some kind of pasta, and the sauce was very thin and watery. She had me taste it, and she said, "This tastes soapy to me, like dishwater," and I agreed.
She also doesn't like to send something back, because having worked years in food service, she also knows what happens to complainers' food in the kitchen, but this was inedible.
When the waitress came back, MrsT apologized, gave her a "I'm sure it's me" line, and asked about ordering something else.
Waitress leaned down, picked up my wife's spoon, got some of the sauce, ate it, and said, "Yeah, you're right. There's something wrong with that!"
Second, very similar story, our favorite Italian place here, no longer open. The food was average, but the atmosphere was wonderful, right out of the 1940's, piano in the bar, bartender was an old woman about 96yo and took crap from no one, very traditional Italian-American menu.
We ordered drinks and MrsT's whiskey sour tasted funny, so she told the waitress, who took it out of my wife's hand, slugged back a huge swallow, shrugged her shoulders and said she'd get her another one.