If I cut and paste an Assembly Combinator, I get the following error when trying to open it:

The mod Assembly combinators (0.6.1) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event assembly-combinator::on_gui_opened (ID 102)
assembly-combinator/script/gui.lua:95: attempt to index field '?' (a nil value)
stack traceback:
assembly-combinator/script/gui.lua:95: in function 'create_custom_gui'
assembly-combinator/script/gui.lua:6: in function <assembly-combinator/script/gui.lua:1>

Thanks for the error trace! I'll take a look

Should be fixed in version 0.6.2. I thought there was only one way to create an entity. Turns out there are several! Updated with all I could find and made sure the programs are copied over when copying or cutting