There was a regression with QoQ relating to $ in column names, due to the hsqldb 2.7.2 upgrade
https://luceeserver.atlassian.net/browse/LDEV-4593
it has been addressed in the 5.4.1.2 and 6.0.0.487 SNAPSHOTS
The old version of HSQLDB was 1.8.0, from 2009, so there maybe some changes in behaviour we can’t change. HSQLDB is used for any QoQ with multiple tables, native QoQ only works on a single table