Just checked myself
– ETS5 “C” (cracked) project with 21 devices imported to ETS6 (N) without problems.
– Exporting the same project works perfect.
OS is Windows 10 just for info.
I do have a project with more than 100 devices (with long history starting ETS1.3, but this requires Compatible mode. Currently running with ETS5C cracked). I’ll try when sinn3r is successful with his smaller project :-)