It sounds like you would be better off making a new post from some scrap of plastic. The super glue and baking soda method works great, but your post is fracturing in a manner that may not be repairable.
15 to 20 years ago I used to restore and refurbish 1960's Aurora Thunderjet HO scale slot car bodies and they had small drilled posts that held the body to the chassis with screws. They were commonly split or broken off. The baking soda, super glue saved a lot of them. I would just fill the hole and them re-drill and tap the threads back in. I also resin casted new posts for missing ones and to adapt bodies that never had posts to the Thunderjet. They would take a pounding and hold up fine.
DAC
15 to 20 years ago I used to restore and refurbish 1960's Aurora Thunderjet HO scale slot car bodies and they had small drilled posts that held the body to the chassis with screws. They were commonly split or broken off. The baking soda, super glue saved a lot of them. I would just fill the hole and them re-drill and tap the threads back in. I also resin casted new posts for missing ones and to adapt bodies that never had posts to the Thunderjet. They would take a pounding and hold up fine.
DAC