I also think that the Tripling / doubling is not takng affect on the test pattern screen.
Correct it does not.
not sure how to enable the tripler, switching it to on didnt do anything .
Linetriple is for 240p/288p sources only.
Whats the cause for this Frequency change and how can we have the OSSC detect this?
Your Xbox is changing from interlace to progressive.
I’d suggest bypassing or disabling your AV receivers scaler, usually there’s a disable/bypass setting.