Loading issues

[Old timer]

870 rem 20 ga combo, New out of the box.
If I hold the fire arm in the horizontal position and rack a shell into the chamber it works great. If I hold the firearm Vertical position and rack one into the chamber it jams with shell 1/2 way into the chamber. take a small screwdriver and click the rear of the shell upwards and it completes the cycle. No problems with ejection. Any suggestions ?

Thanks ;Old Timer

[Synchronizor]

What length shells are you using when the problem occurs?