Hi Pierre,
thanks for you answer!
I tried picard GatherVcfs
java -jar $PICARD_HOME/picard.jar GatherVcfs I=35.vcf I=36.vcf O=all.vcf
The VCFs have the same sample IDs but in different order:
bcftools query -l 35.vcf
14 11 13 12 3 6 10 7 9 5 8 2 4 1
bcftools query -l 36.vcf
5 9 11 13 2 7 12 6 10 14 4 3 8 1
I get an error message from plink saying that the sample IDs don't match. However it can't find any unique names, which makes me think that the problem is, again, the order..
There was a problem with gathering the INPUT.java.lang.IllegalArgumentException: VCFs do not have identical sample lists. Samples unique to first file: []. Samples unique to 36.vcf: [].