OP Breathe, as you can see by reading all the replies many of us, probably most of us have had this problem at one time or another.
I have not seen this comment.
My 20+ year old Kenmore - made by Janome - always shreds thread if I mix poly and cotton thread. It was never the needle, tension, threading, just a mix of thread types. Of course I forget at times, but she reminds me pretty quick.
I have not tried mixing thread types on my new Janome 2030.