I had a similar issue recently trying to clip and export a point shapefile to import into PostGIS. Shapefile was PointZM/Multipoint and I could clip but not export (ogr2ogr failed). These steps ended up working but I can't say why:

• Export original shapefile by explicitly selecting "Geometry" in the Export menu as Point and select "Force Multipoint" but make sure "Preserve Z-coordinates" is unselected to get rid of the Z values

• Export the new shapefile by the same process but unselect "Force to Multipoint" (and "Perserve Z-coordinates") to create a Point layer

This gave me a successful shapefile export that I was able to import into PostGIS.

I had a similar issue recently trying to export a Multipoint shapefile from QGIS to import into PostGIS. Shapefile was PointZM/Multipoint and I could clip but not export with default options(ogr2ogr failed). These steps ended up working but I can't say exactly why:

• Export original shapefile by explicitly selecting "Geometry" in the Export menu as Point and select "Force Multipoint" (this is what allowed it to export successfully) and don't select "Preserve Z-coordinates"

At this point I had a shapefile but it would not successfully import to PostGIS with shp2pgsql. The following steps worked:

• Use SAGA "Multipoint to Point" tool and export the result as a shapefile

• Use shp2pgsql to import into QGIS