Placement cannot find a legal solution

Hmm, that doesn't really look like a standard case of overutilization, but I guess since the logic utilization is being reported as less than 1% in the fitting report, your kernel might be overutilizing logic and the number might be overflowing in the report.

Is there anyway you can reduce the area usage of your kernel to get a proper estimation of the actual area utilization after placement and routing? e.g. by reducing unroll factor or SIMD size? After all, the estimation by aoc is generally not very accurate and I have seen differences up to 50%; though aoc pretty much always overestimates the area utilization for me.