Hi.
The final question first: Is there a reason, that Autoit doesn't clean up RAM usage as a standard feature?
This posting by @guinness was pointing me to the solution for solving my problem:
https://www.autoitscript.com/forum/topic/131315-accumulating-memory-usage/?do=findComment&comment=914208
DllCall("psapi.dll", "int", "EmptyWorkingSet", "long", -1)
this simple, single line called on a regular basis stopped the script consuming more and more RAM.
CU, Rudi.