diff --git a/qpms/qpms_c.pyx b/qpms/qpms_c.pyx
index e64d3d3..5183941 100644
--- a/qpms/qpms_c.pyx
+++ b/qpms/qpms_c.pyx
@@ -1260,6 +1260,10 @@ cdef class Particle:
         def __get__(self):
             return <uintptr_t> &(self.p)
 
+    cdef qpms_particle_t cval(Particle self):
+        '''Provides a copy for assigning in cython code'''
+        return self.p
+
     property x:
         def __get__(self):
             return self.p.pos.x
@@ -1306,6 +1310,7 @@ cdef class ScatteringSystem:
         cdef qpms_ss_tmi_t tm_count = 0
         tmindices = dict()
         tmobjs = list()
+        self.basespecs=list()
         for p in particles: # find and enumerate unique t-matrices
             if id(p.t) not in tmindices:
                 tmindices[id(p.t)] = tm_count
@@ -1323,7 +1328,7 @@ cdef class ScatteringSystem:
             for tmi in range(tm_count):
                 orig.tm[tmi] = (<CTMatrix?>(tmobjs[tmi])).rawpointer()
             for pi in range(p_count):
-                orig.p[pi].pos = particles[pi].p.pos
+                orig.p[pi].pos = (<Particle?>(particles[pi])).cval().pos
                 orig.p[pi].tmatrix_id = tmindices[id(particles[pi].t)]
             self.s = qpms_scatsys_apply_symmetry(&orig, sym.rawpointer())
         finally:
diff --git a/qpms/scatsystem.c b/qpms/scatsystem.c
index 05eb614..c917cd6 100644
--- a/qpms/scatsystem.c
+++ b/qpms/scatsystem.c
@@ -433,6 +433,7 @@ qpms_scatsys_t *qpms_scatsys_apply_symmetry(const qpms_scatsys_t *orig, const qp
         for (opj = 0; opj < ot_current.size; ++opj)
           if (current_orbit[opj] == pj) break; // HIT, pj already on current orbit
         if (opj == ot_current.size) { // MISS, pj is new on the orbit, extend the size and set the T-matrix id
+          current_orbit[opj] = pj;
           ++ot_current.size;
           ot_current.tmatrices[opj] = ss->p[pj].tmatrix_id;
         }