The issue is when adding a field to a module, there is no option to turn off inline edit and when you make changes to the field using inline edit, it deletes all the data. So the easiest solution here is to disable inline edit.
@Matt all the links in the old-forums format https://suitecrm.com/suitecrm/forum are currently broken.
Discourse has a purpose-made functionality to translate those old links to new link, that was part of the migration work, but you need to configure something in the suitecrm.com domain to point those URLs at Discourse, otherwise it won’t work. Somehow that got de-configured a few months ago.
I don’t recall the exact URL formats, but I am guessing it should be
https://suitecrm.com/suitecrm/forum
and https://www.suitecrm.com/suitecrm/forum
@SergeyP you can find those old posts migrated to the new forums if you search for the words in the title, in this case “disable inline editing for lead name field”