A group of Microsoft Products and technologies used for sharing and managing content, knowledge, and applications.
We've ran into this same issue on one of our customer's tenants, it seems to be related to the offline synchronisation in Microsoft Lists.
A temporary fix we found is to go into the Advanced Settings page for the list and set 'Allow items from this list to be downloaded to offline clients?' to No. This setting was also labelled 'Allow people to sync this list to their computers with Microsoft Lists and access it in the browser without an internet connection?' at one stage too, but seems to have reverted back.