The phrase "about one occasion" is correct and usable in written English.
It can be used when referring to a specific instance or event in a general way.
Example: "I remember about one occasion when we went hiking and got lost in the woods."
Alternatives: "regarding one instance" or "concerning one event".
"That's been a really smart thing that we implemented – who knows drug addicts better than drug addicts?" She tells me about one occasion when she "went after" a Detroit woman she'd read about in the paper.
Dynia spoke about one occasion when she tried to return to her home for a shower and described how her son became "paralyzed with fear," and lay down on the ground refusing to move as shells started to fall around them.
He continued, "It wasn't perfect by any stretch of the imagination, and it's not on the same level as the occasional brilliance that South Park reaches on about one occasion per season nowadays, but it's the most fun I've had watching the show that didn't involve a Star Wars parody in many years".
Writer quotes what he wrote about Woollcott on one occasion.
(His Bible-spouting father crept into his bedroom to rage about sin, on one occasion while brandishing a long knife).
My soldiers told me about it, and on one occasion when I was going past there, about the beginning of January 1942-it could also have been at the end of December 1941-I saw.
An uninvited Federal Bureau of Investigation agent questioned me on one occasion about my difference of opinion with Oppenheimer over developing the H-bomb.
The accused stated that in all he had struck about three PWs, on one occasion in order to have the PW leave a dangerous spot; however, he struck no other PWs.
On one occasion, about nine months into filming, one of the adolescent males walked around the back of the vehicle I was sitting in, and as I was on the radio at the time I hadn't seen him coming.
"She talks brilliantly about music," he wrote, "on one occasion giving a pre-concert talk about the Schoenberg piano concerto that would have melted the stoniest heart".
In addition, Judge Collyer's ruling provided further details about a disclosure last week that on one occasion in 2016, an F.B.I. agent working on an ordinary criminal case — as opposed to a national security matter — had conducted a search within a repository of raw emails gathered by the program and pulled up something to read.
