Wren Wiki

When NOT using ASIO, in the device selector (main menu: setup/Audio devices) use a buffer size like 2048. You can set a buffer size of zero, in which case the PortAudio DLL will decide on a buffer size.

When using ASIO the buffer size setting is ignored, and the size recommended by the ASIO driver is being used instead. So for ASIO you will need to set the buffer size from the ASIO control panel (and should set the buffer size in Wren to 0).

Your patch may be too complex, have a look at the CPU percentage next to the module selector, at around 80% things can become critical, enlarging the buffer size may help, lowering the Sample rate and/or enlarging the Control decimation in the Settings Screen F3 may help.