Screensaver closes after seconds only.

[PaBear]

I run OS X Sierra 2016 on both an old MacBook (2009) and an i-mac (2011) & have noticed that 'screensaver' only runs for a few seconds on both machines.
Also, the setting for desktop background/picture is not stable. After setting (in sys prefs) it soon reverts to the Sierra mountain picture (the first one shown) on all or most of the 5 desktops I have enabled. This was also the case under El Capitan. Anyone got any ideas why these items should be happening?

 

[oldscribe]

Hi,

Are these your own creation images or the shipped Apple ones?

 

[PaBear]

Hi,

Are these your own creation images or the shipped Apple ones?

I use both the provided Mac pictures as well as a wide range of my own pictures from Photos.
Another odd effect is noticed when I click on random picture selection. It initiates an immediate change of the background picture. The Pogue Missing Manual not much help.

 

[oldscribe]

Hi,

Sounds like you have some process running somewhere that is causing an interrupt. The trick is to figure out which one is doing it.