I have a Brother embroidery machine, and it makes running stitches between some lettering. It seems to have to do with spacing. When I use a small font it makes the running stitches, and larger fonts have one jump stitch.

Do you have Embird? If so you can change those running stitches to floating stitches.
In alot of designs you can also delete them completely.
Embird is a great program.

There is no problem with that, It is better to trim the thread while it is longer than 3mm. If you need to learn more about this, please contact me by email.

Here is a link that might be useful: Atomic Embroidery Digitizing