This is a well known (long standing) issue. Documented in the code base in commit eea02be70ee37b845f2719b3c08e5baf4b6f51f6.

Countless intermittent sanitizer warnings can be attributed to it.
pnode->nLastSend = GetSystemTimeInSeconds();
            pnode->nSendBytes += nBytes;
            pnode->nSendOffset += nBytes;
            nSentSize += nBytes;
            if (pnode->nSendOffset == data.size()) {
                pnode->nSendOffset = 0;
                pnode->nSendSize -= data.size();
                pnode->fPauseSend = pnode->nSendSize > nSendBufferMaxSize;
                it++;
            } else {
                
                break;
            }
        } else {
            if (nBytes < 0) {
                
                int nErr = WSAGetLastError();
                if (nErr != WSAEWOULDBLOCK && nErr != WSAEMSGSIZE && nErr != WSAEINTR && nErr != WSAEINPROGRESS)
                {
                    LogPrintf("socket send error %s\n", NetworkErrorString(nErr));
                    pnode->CloseSocketDisconnect();
                }
            }
            
            break;
        }
    }
    if (it == pnode->vSendMsg.end()) {
        assert(pnode->nSendOffset == 0);
        assert(pnode->nSendSize == 0);