I have three computerized Vikings sewing machines and a computerized Viking serger, and none of them are picky about thread. They have all taken anything I've thrown at them. For the D1 and 1+, and the serger, which all have the sewing advisor I never have to deal with the tensions. On the Rose I do have to set it to whatever I am doing as it doesn't have the sewing advisor, but once I have it set I don't have to touch it again. I use anything from C&C to Sulky to Maderia to Gutermann to RA and have been recently experiementing with different weights. I would not want to worry about a machine that is finicky about thread; I think I would take it back or sell it.
-Irene