I've seen complaints about this before, but it's another extraordinarily irritating "feature" of x3 that every time you open PRV the controller lane setup that you spent long minutes fixing is gone and the default unusable tiny strips, one per every controller ever seen, is back. 

update for anyone who finds this post and looking for help:   someone posted about this earlier, and it's a useful workaround for the silly controller lanes design. 
 
In a given Piano Roll View (PRV) the very top left corner where you'd think the standard Windows Restore, Minimize, etc would be, it looks like a chunk of a piano keyboard, some programmer, maybe feeling guilt at the bad design, stuck in three extra options:  "Disable Floating", "Dock (ugh)" and "Lock Contents".   With "Lock Contents" you can freeze the controller set up for this window, as long as you never close it.    Then you can open additional prv windows for other tracks (and fuss with the controller lanes there ...) and work without losing the original controller lane set up.    As long as you have enough space and power to keep track of all the windows, it improves the workflow over re-setting the controllers over and over and over.