V3.1.1.0 I pasted in some cells from Excel, adjusted the border colour and quit. When I reopened the table column widths had all changed. I reproduced the error. At the top of the image below is shown the correct pasted column widths, and below, the widths as they are immediately on reopening the project after quitting Scrivener.
Note also the overwriting on the line numbers on the LHS - this occurs when there are multiple lines with cells and is possibly related to the Table Property Dialog having completely lost track of how many rows there really are (the selection in Excel had 179 rows)
Alas a table of all the wonderful things in Scrivener would not include itself. Which is a great shame because I’d like to rely much less on Excel, Word etc.