that happened to mine, but it was an 07, and it was very outta true also. is yours still true?
when you put your cranks on, make sure you dont put them on so that the spot you’re dropping on is where the rim seam is. like i prefer my rim seam at 3oclock or 9 oclock or so…it can be like 4/10…as long as your rim seam wont be on the bottom with your cranks horizontal… i avoid putting it at 12 also because sometimes i’ll land in my non natural crank position…putting the seam right on the dropping spot…
I would check the wheel tension. If it is properly tensioned it should keep the gap from getting bigger. I don’t know if there is much to this, but in the old days there was a theory that the lacing should be such that the spokes will pull the seam together. In order for this to happen you would want the seam to be in the middle of a spoke group (2 pairs of crossing spokes one on each side of the wheel). You can check to see if your wheel is built that way, but like I said I don’t know how much that matters.
.2mm is very small, I have seen much larger gaps (1-1.5mm) on old Rigida road bike rims, and they were fine.
I guess that might help too, but what was refering to is where the seam sits related to the spokes. When you build a wheel you want the valve stem between spoke groups so that you have better access to the valve for inflation. You want the seam in the middle of a spoke group to effectively pull the seam together.