There were, but the others were not of a linguistic nature.
There might be one where the train, which is from Victoria to the South Coast, is described as being loco-hauled by an "electric engine". I noticed that when first reading the book aged about 11, as I knew that by then, the mid-70's, all such services were EMUs, but I recall thinking that perhaps they had used locos 15 years earlier. I still don't know today whether SR ran any loco-hauled services into Sussex in 1961.
The next one arises when some coaches are detached at an intermediate station, and are then shunted into sidings without a staff member checking that there were no passengers still on board. This leads to two boys finding themselves marooned in the sidings. I recall being surprised by this on first reading it, as it seemed highly implausible. While I had not been around in 1961, it seemed to me even as an 11-year-old that surely someone would check coaches were empty before shunting them into sidings.
As the author, Anthony Buckeridge, generally stuck to realistic events in his fiction, rather than featuring impossibilities, this struck me as different from the rest of his work.
The last, and really unbelievable, was that when the two boys marooned in the coaches in the sidings alerted the crew of a shunting engine to their presence, the crew carried the two boys in the cab back to the nearest station and then arranged for them to complete their journey in the brake-van of a freight train going that way.
That seemed wholly unbelievable to me as an 11-year-old. It seemed to me that the boys would either be escorted out to the road and left to walk, or perhaps driven back to the station by road, not conveyed in a shunter's cab, and when they did get to the nearest station they would be put on the next passenger train, not given a ride on a freight train. I recall being quite puzzled that the normally realistic Buckeridge should include such events. However, having read here about shunter crews on lines like the Wenford branch giving enthusiasts cab rides as late as the 1980's, perhaps I was wrong and such a thing could have happened in 1961.