Bridge failed for two arbitrary channel

when hold context execute it Set(_MyCallBridge=${BRIDGEPEER})

-- Executing [1111@XPhone_Hold:1] Set("SIP/101-08508628", "_MyCallBridge=SIP/360net-084dd170") in new stack
-- Executing [1111@XPhone_Hold:2] MusicOnHold("SIP/101-08508628", "") in new stack
-- Started music on hold, class 'default', on SIP/101-08508628
-- Executing [1111@XPhone_Hold:1] Set("SIP/360net-084dd170","_MyCallBridge=SIP/101-08508628") in new stack
-- Executing [1111@XPhone_Hold:2] MusicOnHold("SIP/360net-084dd170", "") in new stack
-- Started music on hold, class 'default', on SIP/360net-084dd170
-- Stopped music on hold on SIP/360net-084dd170

when these values(in red) set it work properly but some time context behaviour is difference


== Spawn extension (XPhone_Hold, h, 2) exited non-zero on 'Bridge/SIP/101-08508628<ZOMBIE>'
-- Packet2Packet bridging SIP/360net-084dd170 and SIP/101-08508628
-- Executing [1111@XPhone_Hold:1] Set("SIP/101-08508628", "_MyCallBridge=SIP/360net-084dd170") in new stack
-- Executing [1111@XPhone_Hold:2] MusicOnHold("SIP/101-08508628", "") in new stack
-- Started music on hold, class 'default', on SIP/101-08508628
-- Executing [1111@XPhone_Hold:1] Set("SIP/360net-084dd170", "_MyCallBridge=AsyncGoto/SIP/101-08508628<ZOMBIE>") in new stack
-- Executing [1111@XPhone_Hold:2] MusicOnHold("SIP/360net-084dd170", "") in new stack
-- Started music on hold, class 'default', on SIP/360net-084dd170


set variable
"_MyCallBridge=AsyncGoto/SIP/101-08508628<ZOMBIE>"
and add 'AsyncGoto/' to prefix and '<ZOMBIE>' postfix to channel and this channel AsyncGoto/SIP/101-08508628<ZOMBIE> does not exits when unHold context execute. why is this happening some times