I think @MissMisc gives solid advice with regards to a lower Apprentice count helping towards keeping down the review tide.
About new lessons unlocking:
If you use WK on a device where you can install user scripts, maybe the Dashboard Progress Pluss script can help. It shows you a visual representation of your current level’s kanji and radical progress towards Guru. If you’re wondering if it’s glitched, this can help you track whether the required amounts of words have been Guru’d.
Something I personally find very useful: Dashboard SRS and Leech Breakdown
It shows how many items are at what SRS stage in your Apprentice and Guru queues. That way I can easily see how many items are at Apprentice 4. If I’m struggling and bumping many items back down to Apprentice 1, I know I’ll have very many reviews coming up, and I’ll ease up on lessons. But if most of my Apprentice queue is 4, I know they’ll be moving to Guru soon - which means they’re on a longer SRS interval, and they won’t be snowballing back to me in the short term.
It’s late, and I’m pretty tired, so I’m not sure that made any sense!
Good luck tweaking things!