QGIS 3.12 issues unknown CRS on vector shapefile layer

I’m trying to export in GeoPDF my map from QGIS 3.12.

After updating QGIS 3.6 to 3.12 can’t recognize the project CRS EPSG 3120 for raster file and vector layer which is the color layer then I tried to reproject both of layers.

The raster was reprojected correctly with the projection EPSG 3120 but the vector layers still with Unknown CSR :

(Unknown CRS: PROJCRS["Pulkovo_1942_58_Poland_zone_I",BASEGEOGCRS["Pulkovo 1942(58)",DATUM["Pulkovo 1942(58)",ELLIPSOID["Krassowsky 1940",6378245,298.3,LENGTHUNIT["metre",1]],ID["EPSG",6179]],PRIMEM["Greenwich",0,ANGLEUNIT["Degree",0.0174532925199433]]],CONVERSION["unnamed",METHOD["Oblique Stereographic",ID["EPSG",9809]],PARAMETER["Latitude of natural origin",50.625,ANGLEUNIT["Degree",0.0174532925199433],ID["EPSG",8801]],PARAMETER["Longitude of natural origin",21.0833333333333,ANGLEUNIT["Degree",0.0174532925199433],ID["EPSG",8802]],PARAMETER["Scale factor at natural origin",0.9998,SCALEUNIT["unity",1],ID["EPSG",8805]],PARAMETER["False easting",4637000,LENGTHUNIT["metre",1],ID["EPSG",8806]],PARAMETER["False northing",5467000,LENGTHUNIT["metre",1],ID["EPSG",8807]]],CS[Cartesian,2],AXIS["(E)",east,ORDER1,LENGTHUNIT["metre",1,ID["EPSG",9001]]],AXIS["(N)",north,ORDER[2],LENGTHUNIT["metre",1,ID["EPSG",9001]]]] – Projected)

Should I reinstall an older version of QGIS ?