When you say you have Gilbert's syndrome, how do you know it? Did you make a genetic test? Is it only because of the high bilirubin in the blood tests? Were you sick with jaundice or some related issue?
I have possibly Gilbert's too. High total bilirubin, conjugated bilirubin is half of the free bilirubin, the doctor said it's Gilbert, I don't have the genetic data to confirm. Never had any problem due to this, *as far as I know*.
Many people have high bilirubin on this forum. A few months ago I spoke elsewhere to someone who claimed to have seen quite many POIS linked to Gilbert's and had a theory about it. In short, problems to break down hormones, notably 3adiol, which then inhibits 5a-reductase and causes low allopregnanolone, GABA-A receptors downregulation, AMPA receptors upregulation and many other consequent problems. I have no idea whether this can be true. As for me, I don't seem to have inhibited 5a-reductase, as I have normal DHT.
Recently I have also read that Naltrexone, an opioid antagonist, could cause high bilirubin as a side effect, so I have wondered if bilirubin problems with Poisers could not be linked to the opioid issues hypothesized by the Chinese doctors in their 2015 POIS paper (see Jiang & alii, Postorgasmic illness syndrome in a Chinese man: no proof for IgE-mediated allergy to semen), and by other people. It may be equally dumb, I don't know.