Biopython BioSQL error : AttributeError: 'DBSeq' object has no attribute '_data'
It's a bug in Biopython 1.78.
What those three sequences have in common is that they're less than 61 characters long.  When you print the record it implicitly calls __str__ for the record, which calls __repr__ for the Seq.  DBSeq gets its method from Seq, which looks like:
    def __repr__(self):
        &quot;&quot;&quot;Return (truncated) representation of the sequence for debugging.&quot;&quot;&quot;
        if len(self) &gt; 60:
            # Shows the last three letters as it is often useful to see if
            # there is a stop codon at the end of a sequence.
            # Note total length is 54+3+3=60
            return f&quot;{self.__class__.__name__}('{str(self[:54])}...{str(self[-3:])}')&quot;
        else:
            return f&quot;{self.__class__.__name__}({self._data!r})&quot;

...and then it only tries to access the nonexistent _data for the short sequences.
So there's a mismatch between DBSeq's lack of a _data attribute and its use of Seq.__repr__.  I don't see a DBSeq class at all in the latest Biopython, so maybe this is fixed already.  But there's no tag for 1.79 yet that I can see and I can't get the very latest code to import successfully so I'm not sure.  In the meantime if you avoid letting repr(record) happen you should be able to work around it.