Hi, I bought a BlackWidow V4 Pro with Razer Yellow switches about 2 months ago. I previously had a Blackwidow 2013, with blue MX switches.
Since the first days, I noticed a very weird behaviour. I use left ctrl + shift to change language, and many times the combination did not work. After some testing, I found out that the keys are actually registered multiple times, since the language bar shows the languages briefly toggling and then toggling back to the original one. This does not happen with the official windows language toggle shortcut, which is Win + Space.
Originally I thought this is due to me not being accustomed to the new more linear switches. I reduced the polling rate, and I thought that it fixed the issue, but it still exists, perhaps to a lesser degree. However, it still remains, and I think that this is a valid issue because it only happens with these two buttons (that I noticed of).
I also found many other tickets for Blackwidow models here, but none was resolved publicly.
This happens both using the Synapse 3 and the new beta Synapse. It does not seem to happen when Synapse does not run.