TPS <20 even with MSPT <50

Just went through and successfully improved server performance by redoing all my configs. Unfortunatly this seems to have caused or uncovered a different issue, I'm getting <20 TPS even when MSPT is under 50!

https://spark.lucko.me/UwE1XofNSh

Any one know what could be causing this? My google searches were inconclusive.

(before anyone mentions it we are planning on updating to 1.21 soon)