Thanks for posting this question on the forum. I have implemented your use-case and not able to reproduce the issue mentioned by you. All the data is successfully inserted, updated and fetched. No issues are seen while viewing the data on the console. I have a few questions for you:
When you are making a PUT request for updating a record in a collection, The JSON body needs to include all entity attributes - both the ones you are updating and the ones that will remain unchanged. The backend will store the entire JSON body exactly as passed in the body. If you forgot to include any attribute here, then that value will be wiped out for that record. Please check this link for more information. Can you please confirm you are doing this correctly?
Can you please tell me if you have enabled any collection hooks on the collection you are trying to insert the data into?
Please review this information and let me know if you still have any additional questions. If you still see any issues then please let me know the steps to reproduce the issue. Also, add "firstname.lastname@example.org" as a collaborator to your environment (GBPlatformDev) so that I can investigate this issue directly into your environment.