Google translator inconsistent behavior for DELETE and SELECT for null values

In teiid I observed following inconsistent behavior:
Q1: select intnum, intkey from smalla where intnum > -10 AND intnum < 20
Q2: delete from smalla where intnum > -10 AND intnum < 20

Q1 returns rows without null values for intnum, but Q2 deletes also rows with null values for intnum.

I observed that if I remove the lower boundary (ie. Q3: select intnum, intkey from smalla where intnum < 20 and similarly for delete), both selected and deleted rows contain null values, so the result is consistent.

The server.log is empty, so I didn't attach it...