With Beyond ATC's new traffic injection feature, planes are landing early on 09L (right at the start of the runway, instead of at the touchdown zone - see below). I spoke to BATC support, and they claim it's an issue with your scenery. I quote their response to me: "they put the start point of the runway at the end of the extended threshold then also specific the threshold length - that is not a valid configuration per the SDK. This is all done because they work around limitations of MSFS for the user flights - but it always breaks traffic"

In addition, some planes aren't taking off properly on 27L. They start to lift off, then they flop back down, and then finally lift off right at the end. BATC said they'd need to investigate this, but I haven't seen it happen at your Stansted scenery, so I'm thinking it might again be due to non-standard implementation of extended thresholds at EGLL.

Quick update. BATC have now come back to me and said that they actually think this is an airport elevation issue. I quote their support person:

"I did try to reproduce both issues and can see it happening - that didn't use to be the case - so looks like a bug has crept in somewhere - looks like the issue is the elevation for the airport is being reported as 5 feet - rather than the 75ish it should be - that messes up all the takeoff calculations. It will also be why they are landing too early at EGLL ini and the flare doesn't happen......it may well be an issue our side at this time - i will investigate further - we also look at the actual ground alt at the airport given by the sim because the values in scenery are often not accurate to what the sim shows."