Lag between stereo receiver speakers and remote WiiM Mini

[SBartnikowski]

Wondering if anyone has experience with music on stereo receiver speakers simultaneously with remote WiiM Mini connected speakers. I am using a CD player attached to a stereo receiver with wired speakers. Output from the receiver is connected to a WiiM Pro Plus. In another room is a WiiM Mini connected via aux to a Klipsch The One powered speaker. The Pro Plus and Mini are connected via WiFi in a multi room environment. There is a significant lag at the Mini (a few hundred milliseconds ?) from the stereo speakers. I set the Group Audio Delay at the Pro Plus to 800 milliseconds, since anything less results in some distortion at the Mini (probably contributes to the lag). Automatic sync only syncs the WiiMs with their respective speakers. I tried increasing the latency via manual sync on the Mini but after about 700 ms, the Mini speaker drops out. Is there a way to sync the audio from the stereo receiver with the WiiM remote speakers ? Or, what am I doing wrong? Or, is this simply not possible? Thank you.