I posted this partially here already, but I’m afraid there’s more to come so I guess a dedicated thread is appropriate.
Happening with Scaler v3.0.1 on a Win10 OS, so far exclusively tested vst3 plugin format.
As mentioned in the other thread, a whole bunch of insert FX plugins are blocking Scaler’s entire audio output. Short example demonstrating it could be found here >> s3 fx block - Sendvid
Affected plugins by manufacturers like:
Arturia (verified “Efx Refract”, “Delay TAPE-201”)
kiloHearts (Disperser, Faturator, FilterTable, many more)
u-he (ColourCopy, MFM2)
iZotope (a few…)
Unfiltered Audio (SILO, SpecOps)
…
…
Just to name a few, the list surely goes on, and of course I wasn’t testing every single plugin. But those are some prominent names, so it’s not like some hobby dev programmed a clunky plugin.
Two freeware plugins (Win & Mac) everyone could test with for example by “Green Oak” are Tungsten and Cesium
Next thing is that trying to insert an FX by certain developers instantly crashes Scaler, as shown below:
Happening for example with everything from “hornet” and “Variety of Sound” (from the example)
There’s most likely more of them again, but I’ve seen enough 
That’s it for the moment.