The first few succeeded, however after the first few successful removals there are errors on subsequent tables re. constraint violations and the overall transaction fails:

# nxdbmgr check
NetXMS Database Manager Version 3.8.314 Build 3.8-314-g9d14b98df7 (UNICODE)

Checking database (excluding collected data):
* Zone object properties                                               [PASSED]
* Node object properties                                               [PASSED]
* Node to subnet bindings                                              [PASSED]
* Interface object properties                                          [PASSED]
* Interface bindings                                                   [PASSED]
* Network service object properties                                    [PASSED]
* Network service bindings                                             [PASSED]
* Cluster object properties                                            [PASSED]
* Cluster member nodes                                                 [PASSED]
* Template to node mapping                                             [PASSED]
* Object properties                                                    [PASSED]
* Container membership                                                 [PASSED]
* Event processing policy                                              [PASSED]
* Network map links                                                    [PASSED]
* Data tables                                                          [PASSED]
* Orphaned data tables                                                 [  12% ]
Data collection table tdata_1124 belongs to deleted object and no longer in use. Delete it? (Y/N)  (Yes/No/All/Skip) a
SQL query failed (2BP01 ERROR:  cannot drop table tdata_1124 because other objects depend on it
DETAIL:  constraint tdata_records_1124_record_id_fkey on table tdata_records_1124 depends on table tdata_1124
HINT:  Use DROP ... CASCADE to drop the dependent objects too.):
DROP TABLE tdata_1124
* Orphaned data tables                                                 [  12% ]
Data collection table tdata_1126 belongs to deleted object and no longer in use. Delete it? (Y/N)  (Yes/No/All/Skip) Y
SQL query failed (25P02 ERROR:  current transaction is aborted, commands ignored until end of transaction block):
DROP TABLE tdata_1126
* Orphaned data tables                                                 [  12% ]
Data collection table tdata_1128 belongs to deleted object and no longer in use. Delete it? (Y/N)  (Yes/No/All/Skip) Y
SQL query failed (25P02 ERROR:  current transaction is aborted, commands ignored until end of transaction block):
DROP TABLE tdata_1128
* Orphaned data tables                                                 [  12% ]
Data collection table tdata_1130 belongs to deleted object and no longer in use. Delete it? (Y/N)  (Yes/No/All/Skip) Y
SQL query failed (25P02 ERROR:  current transaction is aborted, commands ignored until end of transaction block):
DROP TABLE tdata_1130
* Orphaned data tables                                                 [  13% ]
Data collection table tdata_1132 belongs to deleted object and no longer in use. Delete it? (Y/N)  (Yes/No/All/Skip) Y
SQL query failed (25P02 ERROR:  current transaction is aborted, commands ignored until end of transaction block):
DROP TABLE tdata_1132
* Orphaned data tables                                                 [  13% ]
Data collection table tdata_1189 belongs to deleted object and no longer in use. Delete it? (Y/N)  (Yes/No/All/Skip) Y
SQL query failed (25P02 ERROR:  current transaction is aborted, commands ignored until end of transaction block):
DROP TABLE tdata_1189
* Orphaned data tables                                                 [  13% ]
<<SNIPPED>>

etc to the bottom:

<<SNIPPED>>
* Orphaned data tables                                                 [ERROR ]
* DCI configuration                                                    [   0SQL query failed (25P02 ERROR:  current transaction is aborted, commands ignored until end of transaction block):
SELECT item_id,node_id FROM items WHERE node_id NOT IN (SELECT object_id FROM object_properties)
SQL query failed (25P02 ERROR:  current transaction is aborted, commands ignored until end of transaction block):
SELECT item_id,node_id FROM dc_tables WHERE node_id NOT IN (SELECT object_id FROM object_properties)
[PASSED]
* Raw DCI values table                                                 [   0SQL query failed (25P02 ERROR:  current transaction is aborted, commands ignored until end of transaction block):
SELECT item_id FROM raw_dci_values
SQL query failed (25P02 ERROR:  current transaction is aborted, commands ignored until end of transaction block):
SELECT count(*) FROM raw_dci_values WHERE last_poll_time>1620602557
[PASSED]
* DCI thresholds                                                       [   0SQL query failed (25P02 ERROR:  current transaction is aborted, commands ignored until end of transaction block):
SELECT threshold_id,item_id FROM thresholds
[PASSED]
* Table DCI thresholds                                                 [   0SQL query failed (25P02 ERROR:  current transaction is aborted, commands ignored until end of transaction block):
SELECT id,table_id FROM dct_thresholds
[PASSED]
100 errors was found, 0 errors was corrected
Database still contain errors
Database check completed

I imagine cascade could be a risky thing to use by default?

I deleted what I could and left the other orphaned tables in there.  Wait for a patch or is there a manual alternative?

Cheers.