How did you export your tags? And are you talking about just UDT parameters, or are you talking about UDT instance tag properties as well?
There's a known "issue" with the using system.tag.getConguration with system.tag.configure when you're working with UDT instance tags. The "issue" (unwanted behaviour) is that getConfiguration returns all overridden properties on tags (UDT definition non-defaults as well as UDT Instance non-defaults) instead of just the overridden properties at the UDT instance level, which is what is copied with a "Copy JSON" on the UDT Instance tag in the tag browser.
Then, using system.tag.configure with the results of getConfiguration will apply these overrides to the UDT Instance tags, effectively dis-connecting every tag in the instance from its UDT definition 