update with select subquery doesn't work with $parent.$current

[adepase]

OrientDB Version: 3.1.9

Java Version: openjdk-8

OS: DockerFile FROM orientdb:3.1.9 (Debian GNU/Linux 10)

Expected behavior

I expect that:

update morph set uLevel = (select uLevel from nvdb where stem = 'ossia' and simpleType = 'conj') where simpleType = 'C' and stem = 'ossia';

and

update morph set uLevel = (select uLevel from nvdb where stem = $parent.$current.stem and simpleType = 'conj') where simpleType = 'C' and stem = 'ossia';

produce the same result (since the where in the update fixes the stem to the same value). At least, unless I misunderstood $parent.$current or something changed between versions and I missed it.

Actual behavior

update morph set uLevel = (select uLevel from nvdb where stem = 'ossia' and simpleType = 'conj') where simpleType = 'C' and stem = 'ossia';

updates 1 record and uLevel value is 2 (as expected)

update morph set uLevel = (select uLevel from nvdb where stem = $parent.$current.stem and simpleType = 'conj') where simpleType = 'C' and stem = 'ossia';

updates 1 record, but uLevel value is null

Steps to reproduce

Well, I hope the above is sufficient, but let me know