Hi,
It is also a difference if you position the cursor to the beginning of the clip and then hit space to play or if you position the curser to the beginning of the clip during play mode for instance by hitting Num 1 to jump the cursor back to the clip during play mode. You can also test this by duplicating your testone and then positioning the curser at the beginning of the first clip. When you then press play and you let the cursor run over both clips, the start of the first clip will sound different then the start of the second clip.
Anyway you’re absolutely right. This artifact is in the mixdown you have attached.
I have pasted the link to this thread in the report. Any further observations and aspects are welcome.
Thank you, 
Greetings,
JHP