I am sorry for the trouble. This might not be a memory problem in your case. Our engineering team has also identified an issue preventing a database migration on your cloud instance from working as it should, so I suspect some deeper problem with your cloud instance unfortunately. I already wrote you an email about this and will get back to you as soon as I know more.
In the meantime, perhaps you can share your workflow? Simply select all nodes on your canvas, then press Ctrl+C to copy the underlying code. You can then insert it here on the forum with Ctrl+V (you can of course redact any confidential values beforehand, just make sure you don’t change the data structure itself).
You shouldn’t have to do that, so I’d say for now let’s wait and see what the engineering team finds out today about your instance. I’ll get back to you on our email conversation once I have feedback here.
For info, thanks to Tom @MutedJam for solving the problem which was coming (very probably) from importing a workflow from the desktop n8n, which was not on the same version as my n8n cloud. Tom told me to desactivate all my workflows and then reactivate them, and it worked!