Disk space overflow while using queue of emails. Big .message files take all space quickly at /app/spool/

Your software
My Mautic version is: 2.16.0
My PHP version is: 7.2.18

Your problem
My problem is: I’m sending simple html email with not big size(max 500KB), but I got overflow of my ‘%kernel.root_dir%/spool’ folder with *.message files that have size about 30MB.

I look at one of .message file and found inside something like Swift_message Object stringified before my html and after. And That object takes ~ 30MB
Does any one now to deal with that?
At the begginning of .message

And at the end another Swift object
It all really takes all space.

Before update to 2.16.0 I didn’t have these problem…

These errors are showing in the log: no error, but all availible space is taken after few minutes of script working

Steps I have tried to fix the problem: I switched of sending of emails with queue, and looks like system works OK, but if I switch it on after 30 sec I have no space on my 30GB VPS…

Could any one help with this?