Today I have been reported this error from the development team. Looking at MSDN
The client was unable to reuse a session with SPID XXXX, which had been reset for connection pooling. The failure ID is 29. This error may have been caused by an earlier operation failing. Check the error logs for failed operations immediately before this error message.
Reviewing previous messages appear messages like, in my case I have the next error and similars;
SQL Server has encountered 2 occurrence(s) of I/O requests taking longer than 15 seconds to complete on file [G:\FAST_DELIVERY_1.LDF] in database [DELIVERY] (30). The OS file handle is 0x0000000000000978. The offset of the latest long I/O is: 0x00000016506800
It seems that there has been some problem with the physical layer, may be the problem was on the server or the NAS. The problem has made the process crashsed possibly also lacks the error handling process. After a while reconnects the process without problems and works fine.
HTH – Antonio NAVARRO