Xapian 1.4.5 "Db block overwritten - are there multiple writers?" with Glass

Hello,
Since the migration to xapian 1.4.X and the migration to Glass, i've
recurrent database corruption errors. I've to reindex my database to make
it works again.

    > DatabaseCorruptError: Expected block 200713 to be level 2, not 1

Theses problems always occur after this error:

    > xapian.DatabaseCorruptError: Db block overwritten - are there
multiple writers?

I've remarked the error occur when i'm trying to get stored values from a
database with a lot of stored values. I can reproduce the error with simple
python2 script i've posted on github

    https://github.com/staverne/xapian_test
    https://github.com/staverne/xapian_test/blob/master/test_xapian.py

The script always works with Chert backend but sometimes fail with Glass
backend.
It look's like the error report here:

    https://lists.xapian.org/pipermail/xapian-discuss/2017-May/009525.html

Any ideas ?
Cheers,
Sylvain