So, I've been having some low TPS problems lately, I got the timings but I don't know exactly how to read the file. RAM and CPU usage wans't high to the point of throttling the server. https://file.io/GHCaJu
I assume you checked with a lag plugin such as ClearLag? Can't help on the file you sent but it would definitely help to check with a clear lag to make sure its not just entities spawning somewhere in some world or chunks loading at a crazy amount. Hope someone can help you out
I read the file. The issue seems to be related to mobs, and chunk loading. I recommend downloading ClearLag (https://www.spigotmc.org/resources/clearlagg.68271/) and setting it to unloadchunks every 5 minutes or so, or when the TPS drops below a certain level. If you want, I can make you this config free of charge, just dm me on discord (SilverSleet645#1203).
Install this plugin. https://www.spigotmc.org/resources/mob-farm-manager-supports-1-7-10-up-to-1-15-hopper-support.15127/
