Fix Office 365 In-place Archive issue

Please read the job description carefully and request only if you are confident you can fix the issue: We have a user who has a lot of emails in the "In-place Archive" and he usually drags emails from Inbox and categorizes them in the Archives, According to Microsoft this has caused the Archives to become full before the "Auto Expansion" can trigger the expansion of archives and he no more can move any emails to Archives. We want to see if you can provide any solution to permanently fix this issue so the archives keep expanding automatically and prevent this issue. Microsoft said something which I don't believe, they said we should not manually drag emails to the archives and to fix this we need to reduce the size of the archives manually, so the auto expansion can be triggered, so they suggested we move about 30 GB of emails from Archives to Inbox. Even if we want to do this, we have another problem: We don't know the size of each Archive folder to figure out which folder to move! Please message me and tell me what you think, of course I don't want you to provide me a solution for free, but if I'm gonna assign this job to you, I need to make sure you can fix it, we don't have time to experiment.