diff --git a/copyparty/up2k.py b/copyparty/up2k.py
index 15ca799c..7349baa7 100644
--- a/copyparty/up2k.py
+++ b/copyparty/up2k.py
@@ -3041,6 +3041,7 @@ class Up2k(object):
             chunksize = up2k_chunksize(job["size"])
 
             coffsets = []
+            nchunks = []
             for chash in chashes:
                 nchunk = [n for n, v in enumerate(job["hash"]) if v == chash]
                 if not nchunk:
@@ -3048,6 +3049,7 @@ class Up2k(object):
 
                 ofs = [chunksize * x for x in nchunk]
                 coffsets.append(ofs)
+                nchunks.append(nchunk)
 
             for ofs1, ofs2 in zip(coffsets, coffsets[1:]):
                 gap = (ofs2[0] - ofs1[0]) - chunksize
@@ -3059,9 +3061,9 @@ class Up2k(object):
 
             if not job["sprs"]:
                 cur_sz = bos.path.getsize(path)
-                if ofs[0] > cur_sz:
+                if coffsets[0][0] > cur_sz:
                     t = "please upload sequentially using one thread;\nserver filesystem does not support sparse files.\n  file: {}\n  chunk: {}\n  cofs: {}\n  flen: {}"
-                    t = t.format(job["name"], nchunk[0], ofs[0], cur_sz)
+                    t = t.format(job["name"], nchunks[0][0], coffsets[0][0], cur_sz)
                     raise Pebkac(400, t)
 
             job["busy"][chash] = 1
diff --git a/copyparty/web/up2k.js b/copyparty/web/up2k.js
index 48927eb7..95ef9b0b 100644
--- a/copyparty/web/up2k.js
+++ b/copyparty/web/up2k.js
@@ -2400,6 +2400,7 @@ function up2k_init(subtle) {
                             'nparts': nparts
                         });
                     }
+                    t.nojoin = 0;
 
                     msg = null;
                     done = false;
@@ -2606,7 +2607,7 @@ function up2k_init(subtle) {
             }
             else if (txt.indexOf('already got that') + 1 ||
                 txt.indexOf('already being written') + 1) {
-                t.nojoin = t.postlist.length;
+                t.nojoin = t.nojoin || t.postlist.length;
                 console.log("ignoring dupe-segment with backoff", t.nojoin, t.name, t);
                 if (!toast.visible && st.todo.upload.length < 4)
                     toast.msg(10, L.u_cbusy);
@@ -2657,6 +2658,7 @@ function up2k_init(subtle) {
                 if (!toast.visible)
                     toast.warn(9.98, L.u_cuerr.format(snpart, Math.ceil(t.size / chunksize), t.name), t);
 
+                t.nojoin = t.nojoin || t.postlist.length;  // maybe rproxy postsize limit
                 console.log('chunkpit onerror,', ++tries, t.name, t);
                 orz2(xhr);
             };