My 2004 honda civic hybrid has 8 spark plugs. The ones in the back of the motor look like they get much hotter and both times I have replaced them, all four in the back were really really loose.
Is this a common problem.
Do you apply anti-sieze (just a tad) and torque them properly? Are you installing them when the engine is cold?
No, this is not common. And it is very undesirable, as loose spark plugs will wobble as the engine fires up and runs, and this constant motion from the compression in the cylinders will damage the spark plug and head threads, and may require even that the head be removed to fix. This needs to be addressed asap.
I don’t have experience w/you make/model, but the only time I’ve had a problem with loose spark plugs was when I didn’t install them per the service manual instructions.