Sideloading of an air cylinder rod will increase wear on the rod bearings (the place where the rod comes out of the air cylinder), the piston seals, and ultimately, if it’s severe enough, on the wall of the air cylinder.
The resulting wear causes a loss of air pressure through worn seals and a loss of force in the actuator. In really bad cases the air cylinder ord will freeze as the piston jams up against the barrel as it extends or retracts.
Consider using an oversized rod when you buy an air cylinder. The oversize rod will have an larger than normal (for that barrel diameter) rod bearing, and this will help reduce sideloading.
Another option is a stop tube. With this you get a longer than needed air cylinder, and at the rod end inside the barrel a stop tube is inserted which prevents the piston from moving all the way to the end of the air cylinder. This keeps a greater distance between the load and the piston, allowing greater resistance to the sideload force.
The most effective remedy for sideload is to remove it! Use flexible tooling connections, and a floating rear clevis on the cylinder mount to allow the cylinder to move from side to side as sideload occurs. This will extend the usable life of your air cylinder.