While I am not 100%, that I found the answer.
I may have found a clue as to what is going on here.
It has to do with two settings.
The user locale, and the Language of English selected for the interface (UI).
See this picture with the highlighted areas:
In this persons Locale: field, the “System” is expecting settings for en-US operations.
This means $ sign instead of Euro, Printer settings in Inches, and type settings in Pica etc.
But, the User Interface, (UI), is set for en-GB…
Ok, now I’m from Canada(eh!), where Canadians had to go through a forced conversion to metric. (circa 1972), so this is how I was able to spot the problem, when the user mentioned 1.27cm. See Gimli Glider to highlight the differences between Metric measurement and US Customary Weights and measures.
If the user changes the Interface to en-US, this will solve (partially) the problem.
Since RTF does not know the difference between UK 0.50 tab stop (in cm) to US tab stop 0.50 in inches, this is where the computer gets lost, and then tries to import the text using what it knows at the time (inches), but then displays stuff in cm, when the text is saved in RTF format.(on UK computers), but on a US computer (there is that locale thing again), the computer thinks everything is in inches and breaks the text.
This is only a proposed solution at this time as it has not been tested (April 2021). I will update this ‘fix’ as I attempt to re-create the problem, and then implement a ‘fix’.(or work around)