I don't see any tie downs across the rear of the bikes.
The bikes will move in the back of the trailer if you don't secure them.
On my bikes (bikes) I use quality 1" ratchet straps (M&R).
I use two from the driving light brackets going out, down and forward
I use two from the passenger floorboard mounts going out, down and slightly forward
I use one (2") wrapped around the rear wheel going rearward.
The two front straps only compress the spring about 1".
My preference is to allow the bike's suspension to continue to work while in the trailer.
I see that you have your bikes pulled down on blocks. I know several that do that, just not my choice. The back end of the trailer really moves a lot and subjects anything in the garage to moving.
On our last trip I tied down our golf cart a little different.
Normally I use two straps on the rear crossed and going out, back and down to about centered on the rear tires.
On the front I normally use two traps pulling left and right.
The last trip I did not spread the two rear straps as far as I normally did to keep access to the beaver tail storage. I also used only one strap in the front wrapping the tire and puling straight down.
The cart had moved enough so that the front wheels were visibly turned from the original loading.