Hi @jaimun ,
I’ve sent you a test version via PM, let us know if this solves the problem for you.
Hi. Thanks, but still the same. the standalone works ok, but both VST2 and VST3 play for only half a second when you preview a preset. 
(in latest Reaper 64 bit)
We have tested this on multiple setups (Windows and macOS) using the latest version of Reaper, and the preview appears to be working perfectly. We will conduct additional tests.