No, unfortunately this didn't make any difference. And I also tried with 1K jetways + the new bglmanx64.dll...
Do you think it could be related to the boarding passengers? Perhaps the CPU power required to calculate this causes the problem. I find that when the passengers start boarding, there are regular freezes for a second or two at a time, which last for about a minute, until around 40 or so passengers have boarded. After that, the textures go blurry and the autogen doesn't load (I can just test this by jumping to an AI aircraft near the airport - with default jetways enabled, everything loads quickly).