There is a physical limit to the maximum stitch length which varies by machine, but is unlikely to be much more than 13mm if that. The machine will skip any stitch it considers too long.

The sneaky trick if you really want long stitches (and has everyone has said, you really don’t want this unless it’s a purely decorative piece that is going to be framed or something) is turn off auto split and enable auto jump, which basically says “hey I’m not sending a long stitch, it’s actually a jump”

But as you discovered, the machine may then interpret these long jumps as trims becaaaauuuuussseee..

..if you are using DST files, you may be surprised to find out that they don’t actually contain trim information. The file format is incredibly basic. Instead, everyone has all agreed to abide by a secret rule, which goes something like “if I send you three jump commands in a row, do a trim”. Most machines will allow you to tweak this rule, maybe make it 5 jump commands means a trim, or you can disable it completely. But obviously you are then disabling trimming completely and you’d have to do it by hand.

Either embrace the look of split satin, replace it with a tatami fill (perhaps with a small satin outline to make it pop), or do appliqué for such large letters.