I using a plugin that my contain polling at 5.4, so i try to remove that.
I try to get import there again running.
Than i will be build a minimal example for 5.5 sometime later in this summer.
On which Version are you ?
I found a infopage in unreal docs about thread safety. Interchange import needs thread safety.
Thats my advice at the current problem for 5.4. What is wrong in 5.5 i dont know at all so far.
In 5.4 Scrpiting you win thread safety for runtime import as long as you dont use delay nodes right befor the import.
I even suspect you are not allowed to use delay nodes at all during the import so it even doesnt matter if its somewhere else happening. Interchange use a sophisticated and very well designed concept that uses worker threads. Somehow its not immune to other asychnronous events like delays.