@Pink_Minx - I just wanted to make a couple of general comments.
I don't think you have given your body long enough to get used to working on its own again, whatever impact the Metformin might, or might not have been having on you. The impact of Metformin builds up in our systems, and for most folks, it could be fair to assume it also trails off over a few days. Additionally, our bodies like to work to routine, and like to run within unwritten parameters. To illustrate that, think of carb flu and the withdrawal many people experience, with some even experiencing false hypos. Those symptoms are because they have pushed their bodies into a new, temporarily uncomfortable zone, and their body is trying to "correct" it to where it has been running for the period before the changes.
Our bodies can also experience, what I call, enzyme lag, whereby our systems are used to metabolising certain amounts of food, in certain ways, and will therefore be ready to pump out certain enzymes on a regular basis. And change to diet or lifestyle (and meds) can mean a change of enzymes could be required to cope with that new situation. That the body doesn't catch on immediately is irritating, but not catastrophic. There is much written about it, and it's sometimes referred to as the "Last Meal Effect". Have a Google.
Finally, you may find that although your insulin resistance has improved it still has a way to go; one way or another - whether by catching up with your body, or perhaps trimming up a bit more might help. I have no idea what your poundage shift has been, or where that leaves you in the BMI stakes, but I did find my body's "performance" improved in notches, as opposed to a a straight line reducing graph. My body would chugg along, then my scores and so on, would drop a notch, then stabilise, then drop.
If you are still carrying any poundage, it could be worthwhile considering dropping a little more to see if that had an impact?
There is no doubt in my mind that the maintenance stage is the trickiest to get right, as we don't want to go yo-yoing in terms of either weight or blood scores. I think I was probably at my most nervous and scared at the point of maintenance; achieving goals was (relatively!) easy for me.
I hope something in that brain dump might help, but don't be too hasty to make big changes.
As always I would be an advocate of documenting what you are doing, so that you have data to discuss with your HCP, if you need to, rather than what could appear to be random thoughts - especially if your HCP is a reduced carb resistor!
Good luck with it all.