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
O:13:“Swift_Message”:24:{s:28:“Swift_MessageheaderSigners”;a:0:{}s:26:"…

And at the end another Swift object
Swift_Mime_SimpleMimeEntity
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?