Large files and a 32bit server environment

Nextcloud, running on a raspberrypi 3 with Arch Linux Arm, 32bit does not seem capable of syncing files over 2 GByte, although both the data dir and the upload_tmp_dir are both on ext4 filesystems which have no such limitation. In the nextcloud log I see:

Sabre\DAV\Exception: HTTP/1.1 500 Error while copying file to target location (copied bytes: 2147483647, expected filesize: -1 )

/usr/share/webapps/nextcloud/apps/dav/lib/Connector/Sabre/Directory.php - line 137: OCA\DAV\Connector\Sabre\File->put(Resource id #536)
/usr/share/webapps/nextcloud/3rdparty/sabre/dav/lib/DAV/Tree.php - line 314: OCA\DAV\Connector\Sabre\Directory->createFile('X17-59885.iso', Resource id #536)
/usr/share/webapps/nextcloud/3rdparty/sabre/dav/lib/DAV/Tree.php - line 130: Sabre\DAV\Tree->copyNode(Object(OCA\DAV\Upload\FutureFile), Object(OCA\DAV\Connector\Sabre\Directory), 'X17-59885.iso')
/usr/share/webapps/nextcloud/3rdparty/sabre/dav/lib/DAV/Tree.php - line 161: Sabre\DAV\Tree->copy('uploads/jr/3765...', 'files/jr/Downlo...')
/usr/share/webapps/nextcloud/3rdparty/sabre/dav/lib/DAV/CorePlugin.php - line 642: Sabre\DAV\Tree->move('uploads/jr/3765...', 'files/jr/Downlo...')
[internal function] Sabre\DAV\CorePlugin->httpMove(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))
/usr/share/webapps/nextcloud/3rdparty/sabre/event/lib/EventEmitterTrait.php - line 105: call_user_func_array(Array, Array)
/usr/share/webapps/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 479: Sabre\Event\EventEmitter->emit('method MOVE', Array)
/usr/share/webapps/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 254: Sabre\DAV\Server->invokeMethod(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))
/usr/share/webapps/nextcloud/apps/dav/lib/Server.php - line 231: Sabre\DAV\Server->exec()
/usr/share/webapps/nextcloud/apps/dav/appinfo/v2/remote.php - line 30: OCA\DAV\Server->exec()
/usr/share/webapps/nextcloud/remote.php - line 165: require_once('/usr/share/weba...')
{main}

I once heard that this might be related to the 32 bit environment, but again, locally, the raspi can handle files over 2 gigs without any problems.

Has anyone a suggestion which knobs I might have to twiddle?

This is a limitation of 32bit php. There are a few 64 bit distros for RPi 3, there was SuSE, others perhaps followed.