It may be irrelevant to your case but something similar on another QRP labs receiver was recently traced to the MS5351 emitting narrow band noise instead ?of a single tone ?carrier on receive LO frequencies which resulted in loud static in the speaker
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Try to listen to the MS5351 receive output signal on another CW/SSB receiver. ? If you have signal strength but no CW tone that¡¯s the issue ?
Bruce Akhurst