I mean if you have --compression-module=7z then the 7-Zip code is being used to create your archives. That code is known to have to have a memory leak:
As another post in that topic states, if you are using --compression-module=zip (the default) but have set --zip-compression-method=LZMA then you shouldn’t be running into that particular issue.
Are your archive files ending in .7z (the above could be the problem) or in .zip (something else could be the problem)?