Debug KBin Messengers

For 1h my instance is hammered at 100% CPU. I just upscaled, but that didn't change anything. I now have a hetzner server with 4 cores and 4 processes for each of the messenger commands. I figured they just have to process a long queue so that makes sense, but only if the queue has an end...
The only thing I found to debug what the messengers are doing is this: php bin/console messenger:stats
which yields the same result each time I run it:

----------- -------
 Transport   Count
----------- -------
 async       100
 async_ap    100
 failed      2152
----------- -------

! [NOTE] Unable to get message count for the following transports: "sync".

Is there a better way to debug kbin messengers?