AttributeError in case COREG_LOCAL.tieP_filter_level = 0

Initializing tie points grid...
Equalizing pixel grids and projections of reference and target image...
Warping progress     |==================================================| 100.0% Complete  => 0:00:01
	progress: |--------------------------------------------------| 0.2% Complete  => 0:00:00
Calculating tie point grid (427 points) on 1 CPU core...
	progress: |==================================================| 100.0% Complete  => 0:03:38
Found 279 matches.
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-20-ee10534e79cd> in <module>
----> 1 CRL.calculate_spatial_shifts()

~/scheffler/python/arosics/arosics/CoReg_local.py in calculate_spatial_shifts(self)
    351                            v=self.v,
    352                            q=self.q)
--> 353         self._tiepoint_grid.get_CoRegPoints_table()
    354 
    355         if self.v:

~/scheffler/python/arosics/arosics/Tie_Point_Grid.py in get_CoRegPoints_table(self)
    429                 warnings.warn('No valid GCPs could by identified.')
    430             else:
--> 431                 print("%d valid tie points remain after filtering." % len(GDF[GDF.OUTLIER.__eq__(False)]))
    432 
    433         return self.CoRegPoints_table

~/miniconda3/envs/arosics/lib/python3.8/site-packages/pandas/core/generic.py in __getattr__(self, name)
   5137             if self._info_axis._can_hold_identifiers_and_holds_name(name):
   5138                 return self[name]
-> 5139             return object.__getattribute__(self, name)
   5140 
   5141     def __setattr__(self, name: str, value) -> None:

AttributeError: 'GeoDataFrame' object has no attribute 'OUTLIER'