Thorsten, I tracked this down to a non-obvious issue with your initial push wherein you specified `Value Unit of Measure` instead of `Value Unit Of Measure`. (Notice the case difference on the word "of".)
Unfortunately due to another issue with Seeq Server, once you push with the wrong case, the signal becomes "tainted" and you can't make any changes to it via a normal spy.push. As you found, you can only archive it with the SDK.
I'm going to add appropriate guards and error messages to spy.push() that prevent inadvertent use of the wrong case, and I'll also log a bug report in our system to fix Seeq Server.