Flipping and alternating an image mid print on envelopes? Cannon Pixma G6020

Hello everyone! My wife has looped me in to try and trouble shoot her printing issue and for the life of me, I cannot figure it out!

We are using a Canon Pixma G6020. We are trying to print on size A7 envelopes. We are printing from a Mac (Macbook Pro). She designed her envelope in Canva and then exported the design as a PDF. When we print 1 envelope, we get it to print in the desired orientation. However, when we print 2 or more, they print rotated 180 degrees alternating (desired, flipped, desired, flipped, ect.....). Sometimes, this process happens and then suddenly it won't do it (desired, flipped, desired, flipped, desired, DESIRED, flipped, ect.......).

Things we have tried: re-installing drivers. Forgetting and reconnecting the printer. Aligned all print parameters on the printer AND the laptop. Alternating orientations of the envelopes (foiled by the inconsistent alternating error). Even printing in a different area on a more stable surface (current table wobbled.