When I did my first oil change, about 3 years ago, I noticed something loose inside the oil filter housing.
It turns out that what is called a 'leaf spring' had come off it's mounting point.
I think it is for holding the oil in the filter, during normal use, and when you come to change the filter, it opens up a drain hole, as you unscrew the filter.
I've read on the forum that some people are having the oil light stay on for a while after starting the engine and presume you could have the same fault because the oil will drain from the filter and possibly not get up to full pressure.
I've done three more oil changes since the first and it was still in position but yesterday found it loose in the bottom again. I've had no problem with my oil light so can only presume it's coming loose when unscrewing the filter but it would have been all to easy to have screwed on another filter without noticing.
Sorry if my description is a bit vague but check yours to see if it's in place properly.

Click image to enlarge

Click image to enlarge

It looks to me to be a spring to hold some tension on the tube that fits through the centre of the filter element.

There's a rubber bung on 'the leaf spring' which covers a hole. I think when you undo the filter for a few turns it opens the bung to let the filter drain.

If I remember I'll have a look at next oil change to see if mine springs off the hole, which won't be for a while now having only just changed it recently.

Will check mine and can't see an issue with removing the oil filter part way through an oil service interval. 2012 TDV8 Vogue (L322)

I was thinking more for the members with oil light problems because they could whip out the oil filter in a few minutes to check.
[Typing the same time as you Jaygee]

Mine's oil light goes off immediately on starting but it might not be nice to have an open bleed hole for the next 10K kms...

I clean mine out every 6monthly oil change, but the spring always stays put.
The plastic inner tube is 50/50, half the time it comes out with the filter and half the time I unclip it to clean.