Make a table, type some text in each cell, then select all cells & change the font face.
Now add a row or column, type into new cell, the new row or column has reverted to the earlier font.
Tested that this does not happen in TextEdit (in case that is relevant), so possibly not a built-in Apple limitation?
(Have found similar font strangeness with bullets, seemingly not in TextEdit, but have not had time to make it repeatable)
I could reproduce this straight away in TextEdit - the fonts reverted to Helvetica, which is typical - Helvetica is the system default font. Is that the font you are seeing in Scrivener, too? Both tables and bullets are built on the same core code (by Apple - tables and bullets are all their code, unfortunately), and both have similar bugs, often reverting to Helvetica or Lucida Grande. These bugs have been in OS X since these things were introduced in Tiger, and both bullets and tables are black boxes, sadly. One day I’d love to hire an extra programmer who could create custom tables and bullets so that we don’t have to rely on the standard ones.
All the best,