If you're on v4.0.0 and upgrading to v4.0.4 doesn't work, let us know in a new thread. Apparently, there is a similar issue in Siemens Firmware v4.0.4, but only applies when multiple connections are being made.
I think the original issue in this thread was something different. IIRC, the way that I was able to reproduce the issue described in this thread was to attempt to read from an Instance DataBlock that contained some tags that were inaccessible. I believe it was fixed in v8.3.1, but we didn't get any confirmation from OP.