The situation is as follows:
I have a Flash-SWF (in which I have programmed a GUI)
I have a 3D-Annotation containing an annotation-script with some functions that can be called from the GUI.
So far so good.
The SWF is added as overlay to a 3D-Annotation. The SWF contains some AS3-Functions, among them an enterframe-event, that keeps repeating an external-interface call to a function in the 3D Annotation-script. It works so far.
It seems something is wrong with the ExternalInterface-Object.
You need to report this to Adobe as a bug. As it happens Acrobat has a fair number of memory leaks. This seems like a pretty minor one, but they should know about it.
OK, I'll do that.
By the way, imho it's not that minor. ~1mb in two seconds sums up to ~30mb/minute, i.e. 2gb/hour. So if you leave your PDF open for some 15 minutes that's 500mb ram down the drain. Considering the file started at merely 30mb that's quite massive.