Comment by VT_Dude

Former communications semiconductor FAE here. We would troubleshoot issued like this all-day every-day for years, usually under NDA before the product is ever released to production. The solutions are routinely as weird as some of the "voodoo" hypothesis tossed around here - wait for it and you'll see. After a while it seems normal that all unverified combinations are broken and the moments of delight are when an unverified configuration completely works.