Almost a year (and several thousand miles) ago, we had new slide toppers installed, and until today they have been trouble-free.
However, today I was driving in an an area with a strong (40+mph), direct left crosswind. Suddenly, there was a flapping noise followed by a loud bang! I pulled off the highway and did a walkaround. Finding nothing, I tried again, with the same result. And again, this time watching my left mirror. This time, I could see the source of the noise: It was the left front slide topper self-extending and billowing in the wind, and then slamming back into the retracted position. This also explains the infrequent banging noises we have heard from time to time, I suspect.
I drove 20mph on the shoulder to exit the highway, and slowly to the nearby campground. Then I pulled up the documentation for our slide toppers, All four have anti-billowing locks. *None* were correctly readjusted when our slide toppers were replaced. I used my collapsible ladder for the very first time on the road today to adjust them (actually, reposition each arm and reinstall the self-drilling screws) so that this cannot happen again. As far as I can tell, no damage was done to the coach or toppers, and the fabric is intact.
Words cannot express how grateful I am that the momentarily-extended topper did not hit anything.
If your toppers have these simple devices, and you have had the toppers replaced, take a minute to walk around your rig and check them. If they are the Lippert anti-billowing devices, the arm on each one should point straight up when the slide is closed. Correctly-adjusted anti-billowing locks will prevent strong winds from deploying the slide topper "on your behalf" while driving.
It only takes an inch or two difference in the length of the topper fabric to render these devices useless without readjustment.
(Edit) Link to Lippert's manuals: https://support.lci1.com/solera-slider-awning