Robert, sorry to hear your problems with the BIAB-VST. Wish I had the fix but I can only offer the following thoughts. The BIAB-VST v4.0 is in a transition state right now ( ya, I know, a bad time for this). While BIAB 2022 has been getting lots of love to stamp out the bugs following launch, the BIAB-VST has seen little to no updates since launch. On top of that, many of the planned feature updates have not yet been implemented. But I believe it is just a matter of time.

The BIAB-ST has always been challenged by mutiple DAWs, so if the prior version was working in FL Studio, there is a good bet they will get it back. So hang in there.

One thing I have experienced with Reaper, which in the past was always well behaved with BIAB-VST, is unusual crashes and poor performance when working with V4 of the VST. But I was able to remedy this with special attention to system setups. For example, a fresh computer boot before the days DAW activites. Also, careful scrutiny of my ASIO audio drivers (even a reload) to be sure they are all tuned up proper. As soon as I took these precautions, the Reaper/VST v4.0 began to perform well together.

Good Luck
Dan

BIAB – 2025, Reaper (current), i7-12700F Processor, 32GB DDR4-3200MHz RAM, 1TB WD Black NVMe SSD, 2TB WDC Blue SSD, 1TB WD Blue, 2 TB SK NVMe, 6 TB External, Motu Audio Express 6x6