I've read a number of threads now and it appears with AI traffic, back to back flights (returning to the original departure airport after reaching a destination) are impossible, as this AI merging of traffic happens causing frame rates to plummet through the floor.

For those that haven't eperienced it, this is what happens when you return to the original departure airport https://imgur.com/zzgWXlF

FPS then drop through the floor and the sim becomes unflyable (incredibly frustrating after a 3 hour flight). Turning off FSLTL or MSFS traffic has no effect.

Doing back to back flights around places like Europe with AI traffic is, what I would consider to be, the minimum you should expect from a sim like MSFS.

Is this an issue that's being resolved or, even better, has someone managed to resolve it themselves?

Hi, some problem here, but  random on my system and not always in the same airport.

Last two weeks I also did many flights back to back to EGLL without problem (having instead a problem, with same modality you have shown, in EBBR)

On my system the occurrence of the problem (not AI, in fact it seems to be random for me, but the problem of the degraded performance below 10fps) has been mitigated going back to DX11

I have been using Simple Traffic and Live On Line Traffic since ST was introduced, never have a FPS problem.