Dear Adrian.
I believe the issue is that you call for the checklist too soon after setting the flaps. Whilst the handle might be correctly placed at 30, the flaps (and slats for that sake) might still be extending. I am aware that the item doesn’t become green, until the flaps are actually in the commanded position, but this could be a sim-snack.
Go ahead and configure a little bit earlier, wait until the flaps are actually at 30 (indicated at the on the EICAS) and then call for the checklist. I’ll bite my old hat if it doesn’t work.