Is %Sn related to de-wetting?, Help!

I'm new in SMT world, and I've got my 1st challenge: I'm having de-wetting issues with a specific IC 160 pins MQFP (six location, failure is random), where one pin has de-wetting (solder reflow OK, and there is evidence of having contact the past and the pin). I have no issues with other chip makers of same pitch within the board. I suspect that the plating of the device is the cause because pin %Sn of is in the 90% range (85% target), thus pushing the temp up to 218c deg aprox to melt it. I am using AlphaM UP78, with a Omniflow7 furnace, Peak 207c. What variable would you try first?. I run out of bagels and theories.... Any ideas are highly appreciated!. Thanks for your time and advise. Luis M.

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