Two odd bits of Photoshop brush behaviour. Can anyone explain?

[juggler]

I quite often get two odd bits of behaviour in Photoshop CC - presumably due to me hitting a combination of keystrokes which amount to a shortcut, but I can't for the life of me work out what I've done or a quick way of undoing it. If you know what I'm doing I'd be very grateful for an explanation. I'm using a Wacom tablet if that's relevant, though I don't always make use of the pressure sensitivity.

1. Opacity & Flow shortcuts swap

Normally, the numeric keys set the opacity (e.g. 1 sets the opacity to 10%) while shift+number sets the flow (shift +1 sets flow to 10%).
Occasionally this behaviour swaps so that shift + number sets the opacity while number sets the flow.

What have I done to swap these over?

2. Scatter setting on current brush changes

I admit, I've not totally familiar with the many things you can do with brushes. I use a few different ones. Sometimes - actually, irritatingly often - the scatter setting seems to change on my current brush so that instead of getting smooth lines I get trails of overlapping dots.

Any ideas?

 

[juggler]

Aha! I've just found the answer to (1) - it's to do with airbrush mode and buildup settings.
https://forums.adobe.com/thread/1080547

(2) is the annoying one..

 

[retrosi]

I have noticed that not all brushes are compatible with all of the extras such as tilt, pressure sensitivity, flow and opacity.
Often I find the ones which are more compatible have a small window open showing their tilt position or similar as an animation.
I realise this isn't an absolute answer but may help with no.2 getting to grips with which will and which won't do certain things etc.