Odd silver mirror result

I've been struggling with this... Changed all chemicals for fresh but glucose on the left works beautifully but propanal and benzaldehyde both form like lipid looking blobs
 
Nope, never! Our results range from text-book silver mirror to a dirty solution/precipitate in the test tube but never seen a blob of gunk.
 
I have tried it with a new bottle (2006!!!!) And it did work. But yes I have brand new test tubes and ones washed with NaOH on standby.... Benzaldehyde had the blob effect too!! ‍♀️
 
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