String stretching messed with my tremolo :(

[heeby1]

Hey, wonder if anyone can help me with this-

I was stretching a new set of strings when i noticed that, whilst stretching, the string block had moved forward, presumably messing up the intonation.
I tried the next string up (G) and again, the block moved forward again from the stretching pressure.

Is this normal? How do i prevent it from happening in the future?

Any help would be much appreciated (Have included a pic with the saddles that moved in the red circle- this was taken before it happened)

Thanks

[Rich]

Uhhhh, tighten the screw?

[giannifive]

I'm confused. Was it just the saddles that moved? Or did something else shift?

If it was just the saddles, all you have to do is readjust your intonation, and after you do so make sure the saddle screws are tight this time! (But be careful not to strip them.)

[darren wilson]

... and lighten up on your string-stretching regimen. You shouldn't have to pull them THAT hard! (Either that, or your saddle lock-down bolts were really loose.)

[Rich]

I stretch that hard, and move saddles all the time, but I stretch before I measure bridge radius and intonate [which is when I tighten the lock down screws] so no biggie