Hi!
I think this is due to the processing of the stylesheet files. I am almost certain that there is an option on the slide or layer settings where you should be able to add maybe a 1-2 second delay for the slide to display a bit later. Can you please check that?
I am not sure if there is any other solution, maybe a custom script, but timing it with the stylesheet processing can get very difficult. The theme might also has a ‘loader’ feature, which usually waits until all the assets are loaded, you should check that as well.