Before pointing the finger at the Toyo, consider that spirit levels, especially oil-filled, are not infallible to error. If you have rubbed (or somebody else has) the spirit levels with a cloth, they will be electrostatically charged and will resist centering (e.g. they'll rush to left or right but won't centre, or be slightly off centre even when everything appears correct). Use an Ilford antistatic cloth or spray to de-charge the levels. I have done this on everything from builder's levels to trailer-beam bullseye levels and it does work. It has also been done on Linhof Master Tek. cameras. Today the same trick has been applied to one of three levels on my Manfrotto 498RC4 ballhead.
Ah I see. Will the charging stay for a while? Shouldnt the charge dissipate after a while?
It sounds like what the spirit levels seem to be doing here, I'll try that