Completely normal, every drone I have ever flown does that including all of the DJI drones. You just need to straighten it in post; very easy if its an image; if its video you just need to keyframe the corrections add a slight zoom to fill the frame and you are good to go.
Sometimes a gimbal calibration right before taking off helps, but I don't even bother doing that anymore...just wastes battery life while you wait for the calibration to complete. If you stick to shooting very precise short video clips which is how I typically shoot video; each clip is so short I don't even need to keyframe the correction since the portion of the clip that I will use is not long enough for the tilt percentage to change.
Have noticed a few times the horizon with the gimbal is not what it should be while still on the ground, or just after takeoff (and nearby). I also have grids enabled in my app display so its very easy to spot issues quick before takeoff. A quick solution that has worked without having to do a gimbal recalibrate is simply land (if in the air) and power off, then power back on, gimbal is as it should be, all is good.