Tailgate bowed?

[67Fleet]

Well, I bowed my nice freshly restored tailgate a little bit last night. Talk about wanting to put your fist through a cinderblock..... I had jacked up the front of my truck w/ a floor jack just behind the front wheel w/ the floor jack, and heard something pop so I walked to the back of the truck and immediately saw my tailgate sticking out further than usual from the rear quarter. Uh-oh. Looked up the bedrail and noticed how much the bed was flexing so I lowered the truck and then went back to the gate. It creased a tiny bit about 16" from the left on the inner side bottom of the gate. _____ insert curswords here. Luckily it's not very bad at all and it'll be easy to fix when my rig goes in for paint in the next few months, but it just ticked me off. Why do these trucks get so much flex?? Is the frame that weak? The gate I have in the attic is bowed pretty badly (it came on the truck) but I always thought it was from shifting cargo in the bed. Anyone else ever experienced this?