Created attachment 199224 [details]
spreadsheet demonstrating issues 1 and 2

the bug report refers to two spreadsheets, one saved in .ods format (1 and 2) and the other saved in .xls format (3)

1. On some cells, the "automatic" font colour has changed from black to white, usually but not consistently if the cell background colour is slightly darker.
for eg. "light red 2". this also effects conditional formatting where a font color was not specified directly, only the background colour. In all cases where a change is observed, the default (automatic) font colour of black has changed to white.  (see the enemies (red background cells before row 1331) and the myplanets (cells ae2 to ae16) sheets in ogameinfo.ods attached for an example of this. versions of calc from early last year did not have this issue)

2. normally the result of right clicking on a cell pops up a context menu which always includes the "format cells" option. however with some cell content with more than one character not recognised as a dictionary word (eg xs, sss pr xxxxxx ), the "format cell" option is now missing from the context menu, making it more diffecult to edit the cell (ctrl-1 still works). (see the enemies sheet cell d1276, r1223, t1176, r1166, r1106 for an example of this. note. it doesn't effect r1137 and r1120 which are not dictionary words)

3. On another spreadsheet, this time saved in  .xls format, a selection of cells lost their date format and center justification, and in some of them; bold format, and also lost custom number format. This didn't effect every cell in the sheet, only every 6 or 7 rows, but not consistantly throught the sheet. If I corrected the formatting and saved it, the formatting correction was lost on reload, unless I changed the saved format to .xlsx 

Attached is the spreadsheet showing issues 1 and 2. I can't attach the sheet showing issue3 as it is a customers and contains confidential info.

All issues were not present on earlier versions of libreoffice going back for many years, but have become apparent on the more recent releasesm eg 25.2.03