I got "The server was unable to save the form at this time. Please try again.” error when I was trying to save new SharePoint list item.

After some troubleshooting found that this issue is closely related to server memory; when a server memory drops below certain level that is we get these type of errors. We can fix this error by making some memory to free by restarting/killing unused processes.

Permanent Fix

Add more memory (RAM) to resolve this issue permanently!

As for temporary workaround, you can try these solutions.

host controller

Reference

www.sharepoint.diary.com