This is very confusing to explain so I may have to do a screen capture for staff to see what I mean. Until then, I'll post this anyway.
When I ctrl click on a mask, it selects the white portion of the mask and automatically switches to marquee tool functionality where I can immediately press the arrow keys to move the selection around without moving the actual mask. That's the behavior I'm used to and expect.
However, this is different when I'm working on a mask within the .psb file of a smart object. Ctrl clicking on a mask there still selects the white portion but it doesn't automatically switch to marquee tool functionality. It stays on move tool functionality, so if I press the arrow keys, it actually moves the portion of the mask that's selected.
Only stranger, it doesn't cut it out and move it like it would if the move tool were active. It just moves along as if the selection has its own white fill and drops that fill onto the mask wherever the selection lands.
This didn't happen before I updated to the latest Photoshop CC (2018) so I want to confirm that this is either a bug or that some new functionality was introduced that needs to be turned off/on in preferences or is just the default behavior now. Like I said, it's easier to show, so I may have to do that later if no one gets what I'm describing. Thanks!
Try resetting you Photoshop Tools. If that does not fix your issue. Try resetting your Photoshop Preferences. With the text tool selected I just ctrl+clicked on a smart Object layer's raster layer mask, Its Vector layer mask and its smart filter mask. With each click the mask selection was made. However, the tool selected remained the text tool all the time. I can nudge the selection but only the selection moves nothing else. I doe not know it the is a new behavior or not. In the past I believe I needed to switch to a selection too to be able to nudge a selection ant the mouse cursor needed to be within the selection. I test CC 2014.
CC 2014 works the sane way I just tested.
It also did not matter if the smart object was or within an smart object and opened as a work PSB file BSB or normal document I could nudge the seletions set.
Okay, thanks for giving it a test! I'll reset things again and if it persists, I'll try to post a screen capture here so it can be seen in case someone notices something I'm missing.