diff --git a/CommandLines.h b/CommandLines.h
index 3107983..0e9152c 100644
--- a/CommandLines.h
+++ b/CommandLines.h
@@ -5,7 +5,7 @@
 #include <pthread.h>
 #include <stdint.h>
 
-#define HA_VERSION "0.19.4-r583"
+#define HA_VERSION "0.19.4-r584"
 
 #define VERBOSE 0
 
diff --git a/gfa_ut.cpp b/gfa_ut.cpp
index cf0ed28..dbc04a2 100644
--- a/gfa_ut.cpp
+++ b/gfa_ut.cpp
@@ -7365,7 +7365,7 @@ void rebuid_idx(ul_resolve_t *uidx)
     init_ul_str_idx_t(uidx);
 }
 
-void shrink_1b(ma_ug_t *ug, uc_block_t *z, uint32_t is_forward)
+void shrink_1b(ma_ug_t *ug, uc_block_t *z, uc_block_t *lim, uint32_t is_forward)
 {
     if(z->ts != 0 || z->te != ug->g->seq[z->hid].len) return;
     uc_block_t bc = *z;
@@ -7377,12 +7377,14 @@ void shrink_1b(ma_ug_t *ug, uc_block_t *z, uint32_t is_forward)
             } else {
                 z->te -= 1; z->qs += off;
             }
+            if((lim) && (!((z->qs <= lim->qs) && (z->qe <= lim->qe)))) *z = bc;
         } else {
             if((!z->rev)) {
                 z->te -= 1; z->qe -= off;
             } else {
                 z->ts += 1; z->qe -= off;
             }
+            if((lim) && (!((z->qs >= lim->qs) && (z->qe >= lim->qe)))) *z = bc;
         }
         if((ugl_cover_check(bc.ts, bc.te, &(ug->u.a[bc.hid]))) && 
                                             (!ugl_cover_check(z->ts, z->te, &(ug->u.a[z->hid])))) {
@@ -7436,7 +7438,7 @@ void renew_ul_vec_t(ul_vec_t *x, ma_ug_t *ug)
 
 void shrink_ul0(all_ul_t *uls, ul_str_t *str, uint64_t id, integer_t *buf, ma_ug_t *ug)
 {
-    uint32_t k, c_k, p_k, cv, pv, bl, i; uc_block_t *xi; buf->u.n = 0; nid_t *np = NULL;
+    uint32_t k, c_k, p_k, cv, pv, bl, i; uc_block_t *xi, *yi; buf->u.n = 0; nid_t *np = NULL;
     asg_arc_t *av; uint32_t nv, s, e, m, d, mm, is_conn; uint64_t *z; ul_vec_t *x;
     if(str->cn < 2) return;
     for (k = 0, bl = 0, c_k = p_k = pv = (uint32_t)-1; k < str->cn; k++) {
@@ -7464,6 +7466,11 @@ void shrink_ul0(all_ul_t *uls, ul_str_t *str, uint64_t id, integer_t *buf, ma_ug
                 is_conn = 1;
             }
         }
+        if(is_conn) {
+            is_conn = 0; assert(k);
+            yi = &(uls->a[id].bb.a[str->a[k-1]>>32]);
+            if((xi->qs >= yi->qs) && (xi->qe >= yi->qe)) is_conn = 1;
+        }
         if(is_conn) {
             bl++;
         } else {
@@ -7514,10 +7521,9 @@ void shrink_ul0(all_ul_t *uls, ul_str_t *str, uint64_t id, integer_t *buf, ma_ug
             x->bb.n = m;
             assert(x->bb.n > 1);
 
-
-
-            shrink_1b(ug, &(x->bb.a[0]), 1);
-            shrink_1b(ug, &(x->bb.a[x->bb.n-1]), 0);
+            shrink_1b(ug, &(x->bb.a[0]), ((x->bb.n>=2)?&(x->bb.a[1]):(NULL)), 1);
+            shrink_1b(ug, &(x->bb.a[x->bb.n-1]), ((x->bb.n>=2)?&(x->bb.a[x->bb.n-2]):(NULL)), 0);
+            
             d = x->bb.a[0].qs;
             for (k = 0; k < x->bb.n; k++) {
                 x->bb.a[k].qs -= d; x->bb.a[k].qe -= d;
@@ -7546,8 +7552,8 @@ void shrink_ul0(all_ul_t *uls, ul_str_t *str, uint64_t id, integer_t *buf, ma_ug
         }
         x->bb.n = m;
         assert(x->bb.n > 1);
-        shrink_1b(ug, &(x->bb.a[0]), 1);
-        shrink_1b(ug, &(x->bb.a[x->bb.n-1]), 0);
+        shrink_1b(ug, &(x->bb.a[0]), ((x->bb.n>=2)?&(x->bb.a[1]):(NULL)), 1);
+        shrink_1b(ug, &(x->bb.a[x->bb.n-1]), ((x->bb.n>=2)?&(x->bb.a[x->bb.n-2]):(NULL)), 0);
         d = x->bb.a[0].qs;
         for (k = 0; k < x->bb.n; k++) {
             x->bb.a[k].qs -= d; x->bb.a[k].qe -= d;