The data table customization (and probably others) tries to aggressively clear out row references that are not valid in the table they point to. This breaks when selecting multiple actors or objects that have different row handle values. It tries to look up the value but fails due to them being different, and then clears out the row because it thinks it is also bad.
No customizations should cause data loss from just viewing them, so this should be fixed to not fix up handles with multiple differing values. It should also be re-evaluated if the fixup code should run at all when the handle is just viewed
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-105000 in the post.