This is a known issue with Duende plug-ins loaded onto DSPs 3 and 4 at 88.2 or 96kHz. The result is the absence of processing and the plug-ins not passing audio. Any plug-ins loaded onto DSPs 1 and 2 will function correctly. This affects both Duende Classic and Mini.
This bug is present in firmware 2.15 which is included with Duende v2.5.2 and v2.4.1 PC software releases. This is fixed in Duende 2.16 firmware but this is not as yet included in any PC software release.
If you have access to a Mac please run the firmware updater included with the Duende v2.5.3 software release to update the firmware to 2.16. Duende can then be used on the PC platform without the DSP bug. This has been tested and works correctly.
v2.16 firmware will be included in the next Duende PC software release.