[pdftocairo 0.62.0] -pdf | pdf2ps - Error: Ignoring spurious ET operator

Ubuntu 18.04: pdftocairo version 0.62.0

$ pdf2ps antrag_exmatrikulation.pdf # no errors
$ pdftocairo -pdf antrag_exmatrikulation.pdf - | pdf2ps - a.ps

   **** Error: Ignoring spurious ET operator.
               Output may be incorrect.
   **** Error: Executing Do inside a text block, attempting to recover
               Output may be incorrect.
   **** Error: Executing Do inside a text block, attempting to recover
               Output may be incorrect.
   **** Error: Ignoring spurious ET operator.
               Output may be incorrect.
   **** Error: Executing Do inside a text block, attempting to recover
               Output may be incorrect.
   **** Error: illegal nested BT operator detected.
               Output may be incorrect.
   **** Error: Ignoring spurious ET operator.
               Output may be incorrect.
   **** Error: Executing Do inside a text block, attempting to recover
               Output may be incorrect.
   **** Error: illegal nested BT operator detected.
               Output may be incorrect.

antrag_exmatrikulation.pdf

Same action on Ubuntu 16.04 with pdftocairo version 0.41.0 completes without errors.