Issue Keeping Cross Cut Fence Square After 5 Cut Method

Good Morning,

Newbie here to both this group and to woodworking.

Does anyone have any tips on keeping the fence square on a cross cut sled while putting in the remaining screws once you've confirmed it square using the 5 cut method?

I built my first cross cut sled and squared the fence using the 5 cut method. I'll get it to .001 or even a few times at .000 and as soon as I install a few more screws to secure the fence to the bottom, I lose my accuracy. I do predrill the holes.

Needless to say, I'm extremely frustrated...though my husband's ecstatic that he hasn't had to split kindling for the woodstove lately. lol

I've watched countless videos on woodworkers building a cross cut sled and using the 5 cut method and at the end, when they've finished squaring, they just flip the sled over and finish screwing it down. I'm curious if they do a retest after to confirm it's still accurate like I do...and if so...what's their secret?

Thanks

Pam