Tajima TMEX 1501 tension / satin stitch looping

Hi guys,
So I have this TMEX C1501. It's pretty wonky in the tension department. It won't sew well (loops on fills) unless you've got the tensions CRANKED in tight, and even still, there's tons of flagging going on. It's VERY strange. It sews REALLY well though, except for satin stitches, or outlines on lettering. Fills are perfect, some satin jumps are beautiful, but others I get tons of looping. it doesn't matter whether I tighten or loosen. It tends to happen more on horizontal, like the inside corner of a "3" or the insides of an "8". I've changed the needles and bobbins, but it doesn't seem to help it. Sometimes it doesn't do it, but then randomly it'll start looping like crazy.

I really don't want to do these full backs on my Melco machines because the sew quality isn't as good and they're only half as fast.

Thoughts?

Thanks!
Tom