I’m so sorry for any frustration you’ve run into and I’d love to help get to the bottom of this. You should be able to copy and paste records from one table to another table, but it sounds like you are running into a problem with a certain field not copying correctly?
Are you attempting to copy over a linked record field? If so you’ll need to create a copy of the corresponding link in another table in order for the link to work properly.
If none of the above helps, could you provide then could you provide more information about your table setup so I better understand the problem you are running into? Screenshots are always amazing too(feel free to DM them to me if that would make you more comfortable).