The TCP connection was closed by the other end without doing a proper DUL association release and before storescu was done. This is the "DUL network closed" error.
This was noticed by DIMSE while trying to read a protocol data value. This is where the "DIMSE Read PDV failed" comes from. Thus, this second error is just a result of the first one.
The second set of error messages would then occur when storescu tries to do a proper association release, which fails for the same reasons in the same way (although I wonder why writing the release request PDU didn't produce any errors).