At least from what I can remember this is a bug.
According to your patch notes for the latest patch, several changes were made to the spell puppet show. From what I have experienced from playing Puppet Master since the patch, it seems that Puppet Show does not work the same as it used to. For whatever reason, as soon as the unit the puppet showed target is attacking dies, the puppet show breaks. This happened to me multiple times in TTM #137695, where the puppet show cancels fractions of seconds after casting.
I hope this is a bug and not how it has always worked, I just do not remember this ever being an issue before with Puppet Master.
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