the post show that the implementation of the ORM / wrapper around postgresql using PHP need some update.
So any wrapper implementation that is base on the old version of postgresql have to perhaps update their wrapper !!!
Sorry i think you are perhaps in the truth i should check if manifold documentation cover database version supported by manifold 9 for any list databases : postgres/postgis, MySQL oracle, MySQL Maria, geopakage .
The problem should be local : i mean a wrapper is local ( many wrappers ?), otherwise it is a protocol issue ( http / IP)!
I ll confirm later ...all need time but your recent post about test an older versions of postgres i think show the problem is on manifold side...
When issue arise : 32/64bit, compiler version,runtime version, application version of each layers ( DLL exe, ) matters....
The manifold documentation about install cover "
union, doc , APIand most important deepl & keyboard shortcut