I have experienced this in past versions and have just finished performing methodical testing to verify the conditions that make the Eye Dropper tool switch between pick up attributes to put down attributes for each of these circumstances. Here's what I've confirmed:
ISSUE 1
In Vectorworks 2016 SP6 and in Vectorworks 2017 SP2 on EITHER Mac (10.11.5) or Windows (10):
Holding the mouse wheel button down while pressing [Ctrl on Windows] or [alt on Mac] then releasing, causes the Eye Dropper tool to switch to the alternate mode, once both are released. This occurs in at least Top/Plan and orthogonal, but I would expect it to occur no matter the view. I believe the connection here (in terms of programming) is that the Ctrl and alt keys are also used to temporarily switch the mode of the Eye Dropper tool.
ISSUE 2
In Vectorworks 2016 SP6 and in.vs 2017 SP2 on Windows ONLY:
Here are the parameters required to reliably cause the mode to switch as it relates to zooming/panning:
WITH the 'Grouping Similar View Changes' ON in Vectorworks Preferences; If you pick up attributes, then zoom or pan *extensively* before OR after putting them down, and then undo twice / until both the placed attributes and the last lot of zooming/panning are undone, the mode switches to 'put-down attributes.'
I've confirmed on Windows only that the similar 'Grouping all view changes' preference doesn't cause ISSUE 2 symptoms, only ‘Grouping Similar View Changes’ does, so you can use the prior to prevent this behaviour.
I believe the reason this doesn't happen on Mac is because the modifier key used to switch the tool mode (alt on Mac, ctrl on Windows) is not involved in the 'undo' key command; command-z on Mac, Ctrl-Z on Windows.
I’ve submitted a bug report covering both the above.