squid assertion error
 

hello minds,
i have 4 squid box's and the 4 on separate networks
with same debian version and libs but 2 of them have assertion error
assertion failed: comm.cc:178: "fd_table[conn->fd].halfClosedReader != NULL"
after this error squid restart automatically ,
this error can happen every 10 min or every 2-3 hours,
after debug i got this ,

New LWP 4677]
[New LWP 4704]
[New LWP 4687]
[New LWP 4702]
[New LWP 4695]
[New LWP 4725]
[New LWP 4697]
[New LWP 4490]
[New LWP 4493]
[New LWP 4473]
[New LWP 4508]
[New LWP 4495]
[New LWP 4460]
[New LWP 4511]
[New LWP 4516]

warning: Can't read pathname for load map: Input/output error.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Core was generated by `(squid-1) -YC -f /etc/squid/squid.conf'.
Program terminated with signal 6, Aborted.
#0 0x00007f609f457165 in raise () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) backtrace
#0 0x00007f609f457165 in raise () from /lib/x86_64-linux-gnu/libc.so.6
#1 0x00007f609f45a3e0 in abort () from /lib/x86_64-linux-gnu/libc.so.6
#2 0x000000000063bcd2 in xassert ()
#3 0x00000000007996b7 in comm_read(RefCount<Comm::Connection> const&, char*, int, RefCount<AsyncCall>&) ()
#4 0x0000000000709f51 in StoreEntry::delayAwareRead(RefCount<Comm::Connection> const&, char*, int, RefCount<AsyncCall>) ()
#5 0x0000000000697b72 in HttpStateData::maybeReadVirginBody() ()
#6 0x000000000069a101 in HttpStateData::sendRequest() ()
#7 0x000000000069adea in HttpStateData::start() ()
#8 0x000000000079610f in NullaryMemFunT<AsyncJob>::doDial() ()
#9 0x000000000079615b in JobDialer<AsyncJob>::dial(AsyncCall&) ()
#10 0x0000000000795dbf in AsyncCallT<NullaryMemFunT<AsyncJob> >::fire() ()
#11 0x00000000007933a8 in AsyncCall::make() ()
#12 0x00000000007968d3 in AsyncCallQueue::fireNext() ()
#13 0x000000000079665e in AsyncCallQueue::fire() ()
#14 0x000000000064df2b in EventLoop::dispatchCalls() ()
#15 0x000000000064ddc3 in EventLoop::runOnce() ()
#16 0x000000000064dbd1 in EventLoop::run() ()
#17 0x00000000006c967b in SquidMain(int, char**) ()
#18 0x00000000006c8d52 in SquidMainSafe(int, char**) ()
#19 0x00000000006c8d2f in main ()
(gdb) ^CQuit