I began using So Fine (poly) on my friend's long arm maybe 10 years ago now? Then I won an auction and bought probably a lifetime's worth of the thread. I now use it for most of my quilting, both piecing and top stitching. t was lovely in my fussy Cranky Bernie machine. It worked fine in my vintage.
My new/current machine I haven't used very much, is a Juki semi-industrial fast straight stitch only machine. It also seems to like the So Fine, both top and bottom.
Short form: Maybe time to try one of the "new" generation of poly threads. They aren't what they were in the 70s or even the 80s.