Zyra bug doesn't allow passive seeds to spawn in the enemy base.
I'm on a pretty crap computer so I cannot record the bug but perhaps someone with better means may be able to. Happens 100% of the time. Saw it originally in Shiphtur's most recent YouTube video then tried it in practice tool and it wouldn't spawn seeds inside the enemy base and once I walked far enough into the enemy base that the passive seed spawn area was completely inside the enemy base I had to walk outside completely for the seeds to start spawning again.