Pamco cot- matress issues

I brought a second hand pamco cot off trade me, still in great condition. I brought a brand new mattress from Mocka to go on it.

The base that the matress goes on seems really weird to me. The slats fit into two long pieces of wood, but the long pieces are higher than the slats. This means the matress sits on the long pieces then sinks in the middle onto the slats. (I hope I have worded this so you understand!)

So far its not an issue as DD sleeps in a sleeping bag and doesnt move and is only just starting to roll.

I thought that babies were supposed to lie on a flat bed, not a sunken one........ Does anyone elses cots have this???

nope, i checked that, it is the same no matter which way is up- plus it has stamped on it 'this way up' lol

Has anyone else got this problem?????? I keep forgetting to ring Pamco to ask if its normal