I am facing this issue now. I'm using a process in Boomi to get the files from "Folder A" and Zip it with the process below, then send it to "Folder B".
The process will run every night at 8pm. However there is a weird behavior happening here. Whenever there is a new zip file send into "Folder B". The oldest zip file in the folder will be deleted. Means that there is only 10 zip files in "Folder B", when the 11th file come in then it will delete the oldest file in the folder to make it 10 files only.
This is the process in boomi:
This is the screenshot of the SFTP: