the random pause is a random value between 5 & 20 seconds I think.
Yes it's normal that it disappears... essentially when an animation has finished playing it unloads. A simple solution is to add a few more frames & use the set individual pause value for each frame & then select the play in random order. That way it will randomly select a frame & play that & then randomly select another frame. The more of the bright frame you add the more chance it will be selected or vice versa. You could of course create a called by other action containing some if queries... say something along the lines of:
set value 'value name' random between x value & y value
if value 'value name' is 1
play animation 'a'
end if
if value 'value name' is 2
play animation 'b'
end if
etc...
The above being a very quick & crude list of action parts. Obviously you would need to create multiple animations inside of the object to select from. The max value of the random value should be the amount of animations you have created.
It's a bit late, which is why I've not gone into much detail, but hopefully this will give you an idea of what you could do? if not then I will provide a better explanation the morrow afternoon.