I am experiencing this exact issue on the NPM 11.5.3 version (Core 1.3).
It was documented for the NPM 11.5.2 (Core 1.2) version as the following link describes:
11.5.2 Network Sonar Import fails trying to import any of the result nodes...
The solution was to install the Core 1.2 Hotfix 6.
However, there is no Hotfix 6 to correct this issue in 11.5,3.
Any idea why this fix was apparently not carried forward in the next release?
>> We are not upgrading to NPM 12.0 in the immediate future, so that is not a viable solution.
Thanks
wtwoott