I remember reading somewhere or from some bros that you could insert a plastic clip/stick at the side to make the connector holding tighter together. Perhaps you can give this a try because your issues related to connection loose.
After last posting my rex ok already,check engine totally off for past 400-500km
Now can feel merc vfc(behr) oohhhmm hehehehe.
Feel very light to go from 0-100kmh.
But still not brave enought to full throthle.
For plastic clip most of the connector burn already, so that thing automatic diy by nature already.
What i scare that 4th body connector inside also burn so both electrode is just hanging as picture above showing the connector after pull out
Scare if full throthle then electricity can jump between them
Wil go to sc to get them fixed