Question: why Maple gives duplicate solutions from solve sometimes?

Whenever I call solve, I now make sure to convert the solution to a set first to get rid of duplicate solutions which could be generated.

Is there a way to tell solve to return unique solution only by default?

restart:
expr:=-1/2*ln(u)-1/4*ln(u^2+2)-ln(x)-C[1]:
sol:=solve(expr = 0,u):
nops([sol])

   8

But there are actually only 4. The other 4 are duplicated

nops(convert([sol],set))

 4

This does not happen all the time,but I noticed it few times now. Is this to be expected?

Maple 2020.1

 

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