High Temperature Solder Paste

We're using 96.5/3.5 high temp solder paste for our production and we're encountering soldering defects particularly non wetting (tombstoning). A technical document I read mentioned that there is a sort of a problem with the wettability of this paste. Is this really the problem. We already optimize the parameters especially in the area of solder paste printing and curing (reflow soldering). Can anybody recommend other high temp solder paste which we can try for evaluation. We're currently mounting 0402 and 0603 components. Thanks a lot guys for your help...

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